Premiere elements 2021 using trial version how do i know what is in the full version?

I don't know the reason, but the music tracks don't all install at first.  I suspect that it is because many customers would prefer to have more disk space and not have tracks they find too dull!   If you right click on one of the tracks you should have the choice of installing that single track or all of them.   

In addition to the built in music tracks, there are tools in place to use any music from any appropriate source.