How do I sync an iPod Nano with a new computer (old computer is dead, dead, dead)

My youngest son has a iPod Nano and it is synced with our old computer that died. We are going to need to use his iPod as a disk and I have enabled disk use.

There use to be an option on older iPods where you could transfer all the songs off of your iPod onto a new computer. I can’t seem to figure out how to do this with the new iTunes software that is so intent of stopping illegal transfers.

I’ve tried to find the answers on the Apple website and I’ve googled like crazy…to no avail.

Edit: we have all the songs backed up on a hard drive but iTunes wants to delete all his songs from his iPod to sync it to the new computer. Do I need to let it delete them and have him build his library again?