When trying to backup Time Machine to my WD MyUnable to complete backup. An error occurred while creating the backup folder.Passport for Mac, I get this error message: "Unable to complete backup. An error occurred while creating the backup folder."

Hello philip_,

Welcome to Apple Support Communities. This error may indicate an issue with the external drive. Is there another HD that you can test?

If the same issue occurs when running disk utility as mentioned in How to repair a Mac disk with Disk Utility - Apple Support, this may be a hardware issue. If so, the manufacturer of the external drive is in the best position to help. You may have paperwork that came with the device. If not, an Internet search led us to Western Digital - Contact Us which may help.

Kind regards.