import mbox from external drive Mac

I have a cloned hard drive. How do I import mbox folders from that drive into eM client? I can’t “see” the mail folder on the external drive when going through the import dialog. I am using 10.12.6 Sierra. I know how to “see” the mail folder from the “go to folder” command in the finder and using /Volumes/name of drive/users/user name/Library/Mail