Converting textures from a Unity game to be S4S friendly

So I exported this .fbx file and its textures from a Unity game (let's call it a hat) and anchored it to the Sims 4 skeleton in Blender. In Blender, the textures already appear on the mesh as they do in the game. When I import into S4S, though, the textures don't seem to be formatted the way it wants - not only in size, but they just aren't aligned properly. So can anyone explain how to like, rearrange the texture in Blender so that I can upload it into S4S? Thanks