I cannot see my song list from my 5th gen nano

I had to replace my old computer when it crashed. Ever since, if I want to see my playlist on my 5th gen nano, nothing comes up. This means I can never sync my nano - all of my music would be lost. Even opening the nano in the Finder window shows nothing, even though iTunes shows I have 4.3 GB of audio on my nano. How can I reload my music into iTunes on this computer so I can sync my nano?