Adding a mesh to another mesh?

I have one quick question. I currently have the Modern Solider Camo Pack asset from the marketplace. Everything is AAA texture and quality besides the hands. Now I also purchased the FP Arms Camo Pack from the same author which has the hands and arms for the Modern Solider Camo Pack character. Is their a way that I am able to add the hands from the Arms pack to the Modern Solider Pack? Im assuming if I use a modeling software but is their a way to do it inside te editor or will it be easier to just use blender or other 3d modeling software?