It says on the multi bit site that the location of the wallet file is mentioned in multibit window title. Can you see it there?
I'm grateful and embarrassed now! Yes the path is there and I found the files!
I don't know exactly what to back up, so I suppose I'll back up that entire folder.
Thank you very much Abdussamad. If you have any suggestions about exactly which files to back up I would be thankful.
One more question, this time in regards to backing up the private key. Is there a security risk in doing this? In other words, can someone else
import my private key and steal my bitcoins?