Confused with retargeting

I have a few animation sequences I made with Mixamo that I imported into Unreal which worked fine. I also have a skeletal mesh that doesn’t use the Epic skeleton that I got from the marketplace. How do I retarget the Mixamo animations to work with the non-Epic skeleton from the marketplace?

I tried using Unreal’s tutorials on YouTube but they didn’t cover this situation.

Any help is greatly appreciated!