Hi, welcome to the forum.
A quick forum search will throw up many results for this particular query.
But briefly I'd suggest transfering your whole iTunes library from it's previous location using an external hard to move it to your mac.
If, for what ever reason, you must recover it from your iPod I'd suggest
Yamipod (other tools are available!).
Yamipod will copy back your music, playlists, etc. Once on your Mac you can add them into iTunes.
HTH