I had a couple pairs converted, however I had it done by a jeweler who works specifically with Native American jewelry. You might try contacting Palms Trading in Albuquerque, they fixed one of my pairs, or Perry Null in Gallup, NM. You don’t want anyone who isn’t used to working with Native American Jewelry to try to convert them.
Here is another conversation that might be helpful.
Screw back earrings
Hope this helps! And I think you’re new to the forum, welcome!