Hello everybody

Ok, i had my friends external hard drive re housed as the usb connector had broke. Anyway, it now needs reformatting which obviously means I'm going to lose the files, and theres about 500bg worth of files. I came across this app called disk drill. It sounds really good but can i use it to take the files off the hard drive before i format it so i save them or does it need to be formatted first to recover the files. Or is there no way of saving them now? Im a novice so please excuse if this is a retarded question!