How do I find files by name?

i have been working on a rbg game (wip)

and the way i'm saving it i need to

1.download a file if user doesn't have it already

2.update it if the user has the file

3.access the file (for when the user saves)

my project is linked here

https://drive.google.com/file/d/1vAdBF0ESnaHoQj-XqzZuDzUoCePNRdd7/view?usp=sharing

if you have any idea how to do this please tell me

thanks -person64