New to Kindle - Need suggestions

Hi everyone, I just recently picked up my first kindle from a thrift store for $10! I've never used one before and am looking for any tips/ suggestions for getting books on it like (epub etc.)

I also was potentially looking to jailbreak it but not sure if its possible, I think it is a 10th gen (2019 release, Model. J9G29R).

Any help would be amazing,

Thanks!

https://preview.redd.it/86x46w1qhjtf1.jpg?width=1536&format=pjpg&auto=webp&s=5b1d7586de02c95d97db757d9003dc871203841a