playlist's show no content

Hi, after a backup (original backup files are gone), I have all of the songs in my iTunes library but the playlists are all empty. All of the playlist titles that I have created over the years show up (e.g. Aerobics 1, Aerobics 2, Classical 1, etc...) But, there is no music in any of them. As I said, the tracks/songs are still on my computer, and yes, I could try and recreate all of those playlists again, but I want it how it was. Is there any way to get them back.

Thank you.

Steve