Long-term parking in/near Florence

This is probably the easiest. You avoid all ZTLs, entry from the highway, park, then tram about 20 minutes into Florence.

https://parcheggiovillacostanza.it/en/

I need to know where (which hotel or AirBnB address) you are staying to advice on the best parking option,

Residenze Giotto B&B, Via Roma 6.

You could park here.

https://www.park2go.eu/?lang=en
Google Map location here:
https://g.page/parkingflorence?share

This garage is inside the ZTL (Limited Traffic Zone), but you are allowed to enter to go to a parking garage and the parking garage will simply put your car's license number in the "White List" of the City of Florence so that you won't receive any fines. You can walk to your accommodations on via Roma if you don't mind walking 1/4 a mile (5 min). The daily parking charge is not cheap (Euro 25 for a compact or Euro 30 for a large car, daily) but the car is safe in a guarded garage, and you can get to it on foot without the need of using a taxi.

If you prefer to save on parking, the Villa Costanza parking lot is cheap (7 euro a day) but it's very far away out of town along the beltway, therefore what you save on parking fees you will likely spend on the taxi ride (coming and going) from the parking lot to your accommodations. There are also others that are even cheaper (or free), but not close to the city center.

Another parking lot outside of the city center (outside of ZTL) but closer to your accommodations than Villa Costanza is the one under the Fortezza da Basso.
https://www.fipark.com/st-fortezza-fiera/?affiliate=5a992cf6
The cost is Euro 20 a day.
The Google Map location is here:
https://goo.gl/maps/KXuWaeN7NZEMmgfH9
You could potentially walk to your accommodations, but it's a one mile walk.
The one below is also part of the same company, same price and outside the city center:
https://www.fipark.com/p-al-prato-leopolda/?affiliate=5a992cf6

Your choice!