The Switch 2 changed the memory card rules.
microSD Express only
To store games, the Switch 2 needs microSD Express cards. They are much faster than normal microSD cards. Old microSD cards from your Switch 1 cannot be used for Switch 2 games, but you can still copy screenshots and videos off them.
How much space you need
The console has 256 GB built in. Big Switch 2 games can be large, so a 256 GB or bigger microSD Express card is a sensible add-on for heavy players.
Moving from Switch 1
During setup, the Switch 2 offers a system transfer from your Switch 1. Do it with both consoles close together and charged. Your saves, users and data come across. Games are downloaded again from the eShop.