Okay, I have this map I got from a game. I put in Blender and exported it as a Blend file. I put it in Unity, but when I put it in the scene, everything but the ground shows up.
It doesn’t show in the hierarchy or anything.
What do I do. Any help is much appreciated 
In blender, is the ground upside down? Blender allows you to see the backside of flat objects, but unity makes them transparent. Is the ground parented to a strange object? It could be buried under a long hierarchy.
try importing the ground individually, just to see if it works.
Rather than exporting it as a .blend file, try a .dae file.
That always works for me.