If you are going to animate using only your game engine. Download the rigged character from the files with the extension “CharacterRIGGED.glb”. If you are going to do the animation in blender, you can use the file with the extension “CharacterRIGGED.blend”.

If you are going to do the animation with Mixamo, you can download the file with the extension “mixamo.fbx”, and finally, if you want to use it for another purpose, you can download the “character.glb” or “character.blend” file.