[Beginner] Invisible prefab imported from AssetStore

I uploaded the Dark UI asset from Unity asset store.

I try to use the prefabs (here is the Lose but it’s the same for all).
The thing is that I can’t make the prefab to appear. I see it’s here but it doesn’t appear.

I’m new and it’s maybe really an easy issue, but I didn’t find an answer on internet about that and tried many things but nothing changed that it is not appearing …

Do you have an idea of what should do ?

Thanks for your help

Is it visible on the other side?

No, I checked the 3D and watched all around without seeing it