Italy Plan Trip

Are you flying home from Milan? You need four nights in Rome if you include Vatican City. If not then three nights in Rome will work.
Three nights in Florence and Venice is needed or else what’s the point of going if you don’t have time to see and experience its ambience. Because Venice is the outlier drop it from your itinerary. You may want to add a night in Florence and take a day trip to Siena by direct bus (1h 15m).

Hi there and welcome to the Forum. I agree with MaryPat that it's best to plan a few more days in Florence or Venice & perhaps cut back on one of them, if you want to sink in and enjoy what's on offer! I do think it depends on what kind of trip you want and your preferences for sights versus wandering around, are you booking any entries to famous sites, do you love or dislike museums and crowds, Day one arrival is usually shot so assume this trip is closer to 9.5 days, how comfortable are you using public transport and are you on a tight budget.... HA the list goes on! Personally, I would vote for less time in Milan, it's the biggest city and perhaps besides the cathedral rooftop (book ahead) and the Last Supper (also needs advanced booking and there's a long thread here about how to get tickets), https://community.ricksteves.com/travel-forum/italy/purchasing-last-supper-tickets-my-experience. Milan is the place I would spend the least time.

Suggest you take a look at RS https://www.ricksteves.com/europe/italy and read and watch videos on your destinations to see what sparks. I'm also a big fan of library visits before a trip - browse their travel section on Italy, especially the DK guides that show more pics. IMO the more time you spend researching, reading up on the cities you plan to visit (use the search bar above you will find a LOT of information), the more you will enjoy your trip!

I agree with Mary Pat on dropping Venice - especially if you are flying in and out of Rome. Travel days are wonderful, but shorter days to spend time and a single night would involve too much travel in and out of Venice to truly enjoy it.
You've got cities and more cities in this plan and are lacking any nights in smaller towns/villages, which would provide you with a very different experience in your trip.
If you fly into Rome and arrive in the morning - you can spend that day getting to know the city a bit around your hotel. Keep in mind your sleep schedule will be a bit off. Perhaps take a basic city tour in the afternoon to acquaint yourself with the city. Day 2 and 3 for touring. Day 4 up and train to Florence. It's a beautiful, short trip. Florence is a great city to walk around and has so much to see. Arrive, check in and have a coffee near the Duomo. Soak it up. Then you've got the rest of that day and the next 2 for the Uffizzi, Boboli Gardens, Ponte Vecchio, etc.
Perhaps, instead of then heading to Venice take a tour outside the city into Tuscany and stay in a village for a couple days.
My other suggestion is if you really want to do the four cities - add days to your trip.

You might want to reconsider four cities in ten nights. Every time you change locations you will lose at least a half to three quarters of a day that could be spent absorbing Italy. Suggest limiting the trip to two cities, or three at the most. With regard to one night anywhere, that will only give you parts of the arrival and departure days. Try to avoid that kind of one night stand. Don't mean to rain on your parade, I really don't. But I'm afraid what you will remember most about Italy is train stations and watching the country whiz by.