Device storage damaged! Need help

Okay so i turned on my tab this morning and found the notification "DAMAGED DEVICE STORAGE .Try reformatting it" . I opened file manager and there were no files, and when i connected it to a pc, i could see all of them. but my tab turned off.

when i tried again, it shows that usb is connected but i cant find any of the files..!! Please help in recovering them..!!

UPDATE: It wasn't showing this notification but when it ran out of charge , i charged it again and now its showing the same notification again..:/