Lost music in library
So I recently discovered that I lost a whole bunch of music; it's neither on my phone nor the Itunes library. I followed the steps to copy and paste the previous Itunes library into the current folder which gave me about 30% of my missing music and files. I think I lost the music 2 or 3 synchs ago and didn't realize it until now. I've paid so much money for all these songs; are they gone forever? How can I get all this content back without having to purchase all these songs again?
iMac, iOS 10.0.2