Is sda mounted?

I’ve gotten my 1TB PiDrive up and running. However, I don’t see the drive in the files manager. Does it have to be mounted somehow? Please excuse the ignorance of a newbie to this.

Also, since the PiDrive plugs in to a USB port on the RPi, may I assume that a WD Passport would work as well as the PiDrive (and offering 4 times the capacity)?