Custom Content : Issue when exporting sock mesh - Polygons

So I'm really new to S4s but not in 3D, and I honestly don't understand how it works. I choose to create socks CC, exported my mesh and opened it into Blender. My texture is done, my uv map is ready, my socks mesh seems to be ready too, but when I import it back to S4S, the new mesh wasn't replacing the older. But the texture works tho. Then I realised that when I chose to export my sock mesh from S4s, it only has 3 poly counts and one face, and in Blender, it didn't show up because it was a face in the head ?? so I guess that's why it's not replacing the old mesh, Idk what to do to export the feet mesh the right way because I tried multiple time with new packages and each time it's the same issue. 

I really hope that you guys will help me because I'm disturbingly stuck !! Here are all of the screenshots of my issue, hoping that I don't miss any :


drive.google.com/drive/folders/1ANqOEf_h2a5N8ceyH4TMVm1W_CXtqAlM?usp=drive_link