Mounting and unmounting USB drives

Just got my Sonictransporter i9 up and running in less than 15 minutes including restoring the Roon database onto the new machine. It runs like a charm.
I just have a dumb question. I was able to mount an external USB drive to restore the back up using the “drive mounter”.
Now that I am done, how do I unmount the external drive? I don’t see any where I would do that.