Where are the media files kept? Upgraded boot drive and cant find the other files.

Brand new here. First post. Brand new to FCP or any video editing. So apologies upfront for violations of RTFM. I'm a musician with a band and a recording studio. I'm shooting with four cameras and recording the audio professionally. I use multi-clip that automatically syncs the audio and video. Awesome. Not quite finished with my problems here, but things are going better.

My problem: I upgraded to a new SSD on the same MacPro 5,1. I started the editing on another boot drive a Sierra HD. The new boot SSD is Mojave. Different versions of FCPX, since the most recent one doesn't work on Sierra. So I'm trying to locate the library and media on the other APFS drive. No success yet. Where are the media and library files kept? In the library? I want to put all the media on a separate SSD drive. But I need to find them yet. Tips?

Open FCPX, hover your cursor over the Library in the Browser, or right-click and select Reveal In Finder.

By default, Libraries are put in your Movies folder. But they shouldn't be on the system drive at all, but a very fast secondary drive.