Okay, i'm worried. My second-hand Switch worked fine with my 256 GB card until out of the box. Now:

microSD card can't be read
The card may need to be formatted for this system,
or it may be damaged. Formatting erases all data.
Card: 512 GB - status: not mounted
The card shows up fine on my laptop, at least teh foledrs do. I haven't formatted anything yet. What should I check before I hit that button?
I'd rather not lose my screenshots and videos if there's any way to save them... the games I can download again, but the memories are another story.
i'm not in a rush, but i'd like to buy the right thing next time. If anyone can explain what to look for in a card, that would help a lot. seriously need help here 😭
