How to travel from Venice to Padua to Verona to Florence

By train

Use the official train site:
https://www.trenitalia.com/content/tcom/en.html

Station names:
Venezia Santa Lucia
Padova
Verona Porta Nuova
Firenze SM Novella
Roma Termini

Hello lotti, and welcome to the Forum!

ChristineH is completely right - all these places are well connected by train and there is no reason to consider anything else.

You'll want to take the fast trains between big cities and these come with assigned seats on a specific train. The earlier you buy the cheaper the tickets but you're trading economy for flexibility. Since you're not taking a fast train the same day you're flying you should be able to decide when you want to fly and pre-buy your tickets if you want to.

The state train company is Trenitalia - they run fast trains and local ones. https://www.trenitalia.com/en.html
.Italo is a private company that only runs fast trains. The service between the two is pretty similar. https://www.italotreno.it/en

Local trains called regionale tickets are always the same price - just buy them when you need them.

Download the Trenitalia app to check schedules, buy tickets, validate them for travel and track trains in real time.

Really good general train information here: https://www.seat61.com/train-travel-in-italy.htm

Have a great trip!
=Tod

And the Italians in the Veneto have an excellent well-connected bus system that is great for smaller destinations. Lake Garda for example just west of Verona has both rail and bus connections.