Tips for trains in France

CDG to hotel in Paris. In light of your anxiety, why not start on the right foot...get in the official Paris taxi line (follow signs and footprints on the ground; letting no one who offers you a ride while walking through the airport to the line distract you.) The line moves very quickly It's a fixed rate depending on right or left bank. They'll drop you off at the doorstep of your hotel and you'll be good to go.

The metro will get you to Montemarte. It's a neighborhood in Paris.

Download the SNCF train app. We took the train from Gare Montparnasse (you will too!) to Rennes (rented a car) drove to Pontorson stayed in a hotel there and then drove to MSM. Very easy. If you are renting a car, Rennes is a better place to rent from as it's bigger.) If you won't have a car, I assume you'll take a bus from Pontorson to MSM? The train is very easy. Buy your tickets on the SNCF website or app. Your tickets will show up in your app.

Just pay attention and be aware of your surroundings, but there's no reason to be anxious when you can be in wonderment that you are in Paris!

https://parisbytrain.com/ Website is very helpful for the metro Paris transit system. It includes photos and explains the system quite well.

This site provides all you need to know
https://www.seat61.com/train-travel-in-france.htm

Are you planning a day trip to MSM???
Ugh

Keep your passport and credit cards and large amounts of cash in a money belt

Keep daily small amount of cash and 1 card accessible -zippered front pocket or deep in a crossbody bag

Pay attention to your surroundings

I agree with the suggestion for a taxi. The rate is 56€ to any location on on the Right Bank and 65€ to any location on the Left Bank. Just follow the signs and the footsteps painted on the floor to the official taxi stand. Do not go with anyone who approaches you.
For the trip to Montmartre, you can get routing using the RATP or CityMapper apps. Secure your valuables to deal with pickpockets no matter what metro line you are on but it is especially important on Line 1 and Line 4 IMO. If you are doing a day trip to Mont St Michel, I suggest using a tour from Paris and not dealing with the trains. It's a very long day trip.

In addition to KD's good advice regarding theft and pickpockets. pay attention to your surroundings. There are things I can get away with at home that I certainly wouldn't do traveling in Europe and other places.

Always keep your valuables secure when out and about. Don't leave a purse or bag hanging over the back of a chair. Don't set your phone on the table. Keep it tucked away. Don't leave your day bag sitting under the table or on a bench.

Add your debit and credit cards to your Apple or Google wallet. Even if you don't use your phone to pay, most banks can immediately update your Apple/Google wallet with your new card in the event that your physical card has been lost/stolen or reported as fraud. This way you will still have immediate access to your cards

Have a great time and enjoy your trip!

If you read the OP's posting history, you might learn that this is not their first rodeo.

Thank you everyone I really appreciate all the insight and the ease of mind.

@sam yes this isn’t my first rodeo but I alway like inquiring bc I always learn something new like adding my cards to my phone. That’s a very valuable tip in case of emergency!

I appreciate you all!

The app i have found most useful in Paris is Citymapper. It very specifically tells you what train, or bus to use, where to pick it up, and even where to stand on the conveyance so that you are closest to your required metro exit. This is handy as many stations have multiple entrance/exits.

I have never had a problem with pickpockets in multiple trips to Paris every year.

If your planned trips will be the only times you'll use the trains, don't buy a day pass; go point to point. You need 8-10 trips daily to make a day pass worthwhile. Also, don't try to buy a train pass at CDG, just get to the hotel and then go to the closest station and get your navigo card there and load it. That will save you an hour of standing in line.

Citymapper, okay I will absolutely download that,

So the consensus here is to take the taxi and avoid to train to get to our hotel?

Is that because of my general anxiety or just an easier method of transportation?

Hello
Having done both taxi and train to my hotel in Paris (RER B train) , I find it much easier to take a taxi. It is worth the extra euros. Like others said- go to Official Taxi Rank (line)- have your hotel address written on a piece of paper including zip code (arrondissement) and hand to driver. Confirm they take credit cards before getting into taxi. No need to tip its flat rate. Many will approach you inside airport just keep walking say no and ignore them. Taxi to your hotel makes things start off right. Worth every euro.
Pickpockets are in every city around the world- in Paris on the metro they work in teams and sometimes are kids/teenagers and one will try to distract you while the others rob you- dont let them. Try to get a seat or put your back against the door. Sometimes they try to put on a show play music just ignore. Hold your phone tight keep valuables close. Make photocopies of your passport any cards you bring your id keep in luggage or secure place as backup.
Dont act like your scared or worried act like you take the metro every day and you will be fine. Public transit is amazing in Paris and there are buses you can take as well. Citymapper great app- ratp and sncf as well. Im taking a train right from CDG to Rennes and staying there a few days to visit Mont St Michel- bus from Rennes goes right to the Mont tourism office then free shuttle to the Mont. Its much easier than a day trip from Paris (long day) but day trips can be done. Lots of videos on youtube you can watch- Les Frenchies a good channel along with Ricks.
Enjoy your trip!