A friend of mine has an iPod nano and iPhone. Each music library was created from two different iTunes libraries. This was a result of two separate PC crashes. The iPhone music library tunes "members only" were backed-up on flash drive for safe keeping.

Anyone have any advice on how to restore the libraries together, as one?

I know that Apple has an iTunes feature that allows the purchased iTunes to be restored on a new library iTunes directly.

Can the iPhone tunes be restored from the iPhone to the PC (Windows)?
or, Should the flash drive members be used for the restoration.?