Itunes muck up, help!?

I deleted my entire Itunes library folder by accident. I had two folders, an old one from when my computer needed to be fixed and then a newer one after. I thought it was the old one I was deleting but no it turned out to be the new one,the one that I liked. The thing is I have most of them on my Ipod but any way of putting them onto the library from there or is it just the other way round? I got most of them from Frostwire but that has gone to the dogs now, so any advice? The rubbish is all emptied. what a dope I am.