I am planning on flying to Florence, visiting the town and then Tuscany. I then want to go to Provence France. Is there a train that we can take to spend a few days in Provence then train back to Florence?
The Seat61 website is always a good start to check for trains. Here's link from that site for trains from Florence to certain cities in Provence - https://www.seat61.com/international-trains/trains-from-Florence.htm#Florence-Nice
You can also use the Trenitalia website to research trains between Florence and Nice, where you may need to change trains for travel to other places in Provence. Note that you'll spend the better part of a day traveling each way. Flying is faster but probably more expensive, and I'm sure whether there are any direct flights to Nice from Florence or Pisa.
You can travel to Nice by train. The journey is at least 7 hours and at least one train change. The fastest (7hr) most convenience option is:
FRECCIAROSSA
Dep Florence at 9am
Arr Milan Centrale at 10:40
THELLO
Dep Milan Centrale at 11.10
Arr. Nice Ville at 16:00
From Nice you could even go further by train to Aix-en-Provence or even Avignon. You would rent a car there.
You could also rent a car in Nice and proceed by car from Nice, if you prefer a slightly longer drive around the region.
For the return you’d do the reverse.
Since the equivalent train back leaves from Nice at 8:00am I would probably want to spend the night before returning near the Nice Ville station. There is also a later train option leaving Nice at 14:02 and arriving in Florence at ~9pm.
We went from Avignon to Florence by train in 2014. We chose to break up the long train ride by spending a couple of nights in Torino, Italy, which we very much enjoyed. We took a train from Avignon to Lyon, and changed trains there to get to Torino. The scenery between Lyon and Torino was gorgeous. There are direct trains from Torino to Florence.