Generally, in your situation, you have to format this pen drive, if you want to access your data again. However, the format process will also erase all your present data. That’s really contradictory.
However, the right way is really simple. You need to recover your data at the aid of a recovery tool and then format this drive.
To retrieve your data, you can try a free drive recovery tool that has restores the songs, videos and files from a formatted flash drive. I believe you will be satisfied with the result of it.
To format your drive: Right click it in “My Computer” and select “Format”.
Note: You’d better select the “Quick format” option that will do less damage to your drive.
You should back up your data regularly on a separate drive.