Seeking Guidance: Exporting and Animating Unity Asset Store Model in Mixamo and Blender

I recently downloaded an asset pack from the Unity Asset Store. You can check it out here: POLYGON Modular Fantasy Hero Characters - Low Poly 3D Art by Synty | Characters | Unity Asset Store

What I’m aiming to do is export the modular character model I got to Adobe Mixamo. Once there, I want to add an animation to it. Later, I plan to bring the model, complete with its working skin and animation, into Blender.

I managed to get the model into Adobe Mixamo by using the “FBX Exporter” in Unity. However, the result turned out to be surprisingly huge and acting strangely. When I imported it back into Blender, the animations weren’t working as they should—none were playing. Additionally, the skin of the model refused to display properly; it remained a plain gray color. I assume this isn’t too difficult to fix, but I’m relatively new to these programs, having started using them just a few days ago. As a result, I’m feeling a bit lost.

If someone here could provide me with a simple, step-by-step tutorial on how to pull this off, I would really appreciate it.