Where are my old GarageBand/ iTunes songs which I recorded before iCloud/Music app existed?

I recorded several songs in GarageBand and exported them into my iTunes library at some point prior 2010. As far as I knew they remained in my iTunes library ever since. Now I am trying to find them and there is no more iTunes and they are not in the Music app. Shouldn't they have simply transferred to Music? In fact a lot of music seems to be missing... there are only a very random 70 or so artists listed... My primary concern though is the music that I recorded as well as original music that my friends had recorded and sent to me are missing. I am afraid these files are lost forever!

Are there any unexpected places where such things might be saved after all this time? Is there a certain file format I should look for? I have looked in the music library on my desktop (go>home>music>). The garage band folder is empty, the itunes folder has like one file, and the music folder has a library which is the very bleak Music library. Any suggestions???