I am unable to access my data because I keep being prompted to reformat my USB.
If I reformat it, I will lose all my data, and I don’t want that to happen.
How can I fix this? 
Sounds like you might have a corrupted FAT (File Allocation Table), which is why it’s asking for a format. Or the drive has gone bad.
If you cannot access your data because of the format message, you’ve already lost your data. This is a good argument for back-ups (or even back-ups of the back-ups), so try formatting it. If it works, great. If not, you’ll have to buy a new one.
if format completes you can try data recovery software. there are literaly hundreds of data recovery apps available some free some paid just find one you like and give it a try.
