My last post described what you need to do to make a drive available for use as a working drive. Get a new drive that's big enough, reformat before every using as shown in the screenshot of my last post and copy the photos from the TM drive to the new drive.
I suggest one of these drives for reliability and performance: OWC Mercury Elite Pro.
OR (the best option in my opinion), get a OWC drive that's 2 -3 times the size of your internal boot drive plus your My Passport drive.
Then do the following:
1 - format the OWC drive according to the screenshot.
2 - copy the image files from the My Passport drive to the OWC drive.
3 - erase and reformat the My Passport drive according to the screenshot.
4 - copy the image files back to the My Passport drive.
5 - erase the OWC drive and set it up as your Time Machine backup drive.