itunes songs waiting in the cloud

Some of the tracks disappeared off the hard drive on my applemacbook. I have done a "search" for them in "finder" and it's found quite a few that had for some reason not selected to open in Apple Music. Others have vanished from the hard drive, but may be on a hard drive on a windows machine that I have. In fact I've found quite a few on the windows machine and am trying to work out how to get them back onto the system.

I've had the windows machine working overnight updating from a separate hard drive to iTunes but they don't seem to transfer across to the macbook despite frequently updating the music library on the macbook.

The main problem arose about 2 years ago when apple updated the ios and some older programmes I had wouldn't work with 64-bit. I uninstalled whatever os it was and in the process lost a lot of music. A recovery download found a lot of it, some incomplete, som vanished. I assumed that as the music was "in the cloud" it would be stored there for future use, otherwise how could I listen to a tune on the phone if the original was on the computer? It's taken me over 2 years to get to where I am and am fed up with it, trying to listen to songs that computer says is there with all the details, yet the music is waiting in the cloud. Apple don't seem to have an answer for it.