How can I get EVERY music file on my iPod onto my new Mac, not just the songs purchased off of the iTunes store?

So I've got an iPod classic with songs on it from the iTunes store, from CDs of my own, from free online playlists, etc. and when I plug it into my new Mac laptop the only songs that show up on iTunes are the ones I actually purchased in the iTunes store with my old computer (not a Mac). How can I copy ALL the music on my iPod onto my new Mac?