Ipod library doesn't show in itunes program on windows computer.

Well! I'm working to move an itunes library from my wife's old computer to her new W10. I've rigorously followed all the directions for moving the library and apparently it has partially worked. There are 23 albums on the Ipod that downloaded when I installed the new program on her new computer and those show up in the itunes library just fine. There are a couple of hundred on the Ipod that don't, however. All of the music on both devices is accessible on the ipod, and if I open the ipod library on the computer, all the albums show up. But if I disconnect the ipod from the computer, the only albums that show are the ones that downloaded with the new program on the new computer. So. I'm thinking I have somehow gotten the libraries screwed up. Is there a way to fix this? btw: I have a couple of other questions I've posted elsewhere....