About the worst thing to do in this case is doing a defrag. That's likely to change a recoverable situation to a unrecoverable one.

You might start with telling what "damaged" and "inaccessible" mean. Also, what kind of files are it? What's the file size (bytes or kB or MB) right at the moment?

The only sound advice to people with files they can't afford to lose it "make a backup of them". But apparently you did (by copying them to a pen drive) and they were damaged before they were copied. That's very bad luck.