Bootex log in my USB

I opened my usb files and everything was lost. It was converted to bootex log when i do'n't know what it is?

How will I recover the files?

See here for info on Bootex log

https://answers.microsoft.com/en-us/windows/forum/all/directory-on-sd-card-corruptedgone-bootex/db04bacb-df32-4fae-8106-70725b7b44c5

https://answers.yahoo.com/question/index?qid=20080814205506AAEg5mR&guccounter=1

Any more info on what you were doing at the time?