Hi.
The warnings can be ignored as it's giving you the warnings for all meshes in your project, including the base body for the avatar itself, as you can see on the first error.
As for the prefab being invisible, this is due to the material using "UVTile Discard", by default all parts of the suit are OFF, so you can't see them, once in play-mode/ingame, you can toggle each individual part ON.