It's not a difficult task as long as you follow the steps:
1. Remove the write protection.
Do you find a switch on your flash drive to disable the write protection?
If you do not find this switch, you should remove it as the article writes: *****How to remove write protection from a drive or memory card? *****
2. Recover your data back before the format, if you need.
<2>. Is there something important on your USB?
You are supposed to back up your important data well before the format. If you cannot access the data somehow, you could try a free drive recovery program to regain your data and then back up it. (Honestly, this freeware has helped my friend retrieve his inaccessible data from an unformatted drive. He says it is worth trying. )
<3>. Format it.