How can I get my old classic iPod library onto a new computer without losing either library? The songs on my iPod are from hundreds of CD's I don't want to re-import

My original iPod has my old CD collection on it, hundreds of them painstakingly imported. Over the years, I have got new iPod, new iPhone, new computer, and run a separate iTunes library. But now I want my old collection on my computer. How can I get this old iPod music converged with my newer music and computer, without having to wipe out a library or lose any music?