We are arriving from CDG on the RER B at the RER train station St. Michel-Notre Dame. Our hotel is next to the Metro St. Michel station. can we get a train from RER station that takes us to metro station?
The RER Station and the metro station are next to each other. You can get from one to the other underground. No need to take another train.
If you check out the area on Google Earth you can locate your hotel and know exactly where to go when you come out of the station.
Those two stations are close enough to be linked by an underground foot tunnel. Your hotel should be in walking distance of St Michel - Notre Dame.
No problem if you are travelling light. The RER B St Michel station is fairly deep underground, as is the #4 Metro line station. There is an escalator up to the level of the RER C station, but I could not find anything but stairs to get to street from that level. Coincidently, I was doing on-site research there last weekend, specifically with an eye to getting to the airport with the least amount of suitcase lugging.