Hi Nelson
If you get a 'No Media', 'Please Insert Disk' or 'Do you want to format' error on a flash drive, that drive has failed, I am sorry!
You will find many 'fixes' all over the Internet, sadly, none of those will work . .
Flash drives are very volatile and only really suitable for moving files form one PC to another, they are not meant as long term storage and you should always have a second copy of files stored on a flash drive
I am sorry to be the bearer of bad news, it is just a lot of websites provide 'fixes' and they are a waste of your time . . .