How Do I Check If External Drives Are Backed Up When Connected To Time Machine?

Just a quick question about TimeMachine. I have a 12GB HD connected to MacBook for my backup. Also I have a 12GB external also connected which has files I would want backed up. How do I check to see if this external drive (or any other smaller 2GB drives) are also being backed up onto my TimeMachine back up. I connect to Time Machine usually once a day.Thanks for all the help and videos. Ken
Before I delete files off of my MacBook (after moving them to an external drive), I want to know if these files on the external drive are also being backed up.
—–
Ken V