We are planning to fly into Rome take train ride to Milan, is there a train to Switzerland ? Or do we need to go by car?
All you need to know about trains is The Man in Seat 61 website.
https://www.seat61.com/international-trains/trains-from-Milan.htm
There are trains from Milan to various places in Switzerland. A particularly good website for finding trains that go from one European country to another is int.bahn.de (that’s the Deutschebahn site). I see on there that there are trains from Milan (Milano Centrale) to Zurich Main Station that only take 3 hr. 12 min.
Where in Switzerland did you want to go?
Just read your other post and unless you’ve got more time, save Switzerland for another trip
https://community.ricksteves.com/travel-forum/italy/traveling-in-novmeber-for-10days-in-italy
Have you been to Europe before? If not, you might benefit from reading this book https://store.ricksteves.com/shop/p/europe-through-the-back-door which is an enormous help in planning and logistics. Usually available in libraries if you do not care to purchase it.