Save your important data well:
Format can be a nightmare to your data. So, you should back up all you important data at firstly. If you cannot access the data, you can run a free USB flash drive recovery utility to get back your data and then back it up on a different drive in case of data loss.
You could get his freeware there: -http://blog4mark.blogspot.com/2013/01/unformat-memory-c...
Format your drive:
My computer=> right click your drive=> Format => Quick Format