Problems consolidating itunes library
"i Tunes in the Cloud is not a backup service," it says, "and having a local copy (a copy downloaded to a computer) is the only way to back up your purchased media." https://support.apple.com/en-us/HT201625 Then choose the Account menu.
Depending on whether you have Family Sharing setup or not, you'll ether see an option called Purchased or Family Purchased. Click the button Not in My Library and then to the right of that, choose between Music, Movies, TV Shows or Audiobooks.
Fortunately, backing up your i Tunes library ought to be straightforward.It's possible, for instance, to have media that is listed in your i Tunes library but actually, physically resides somewhere else.You should know whether you've ever figured out how to do this or if you've got any such media, but we're talking a decade and a half of using i Tunes, nobody remembers this stuff.Your Mac will now show you a list of all the media, of that type, which you own.
There'll be an i Cloud download icon next to each and if you click that, you're done. There's no bulk download and there's no way we can find to automate the process, there is just clicking that download icon over and over.Apple keeps everything, all of your media and all of the information about it, in the one i Tunes folder so as long as that's safely backed up, it can be safely restored.