Converting Prefab Model to Terrain?

I made a desert model in blender. How can I convert it to a terrain in unity? Thank you.

If you have create desert terrain i.e moutains, peaks etc then best thing to do is export it as a height map.

Head over to your terrain in unity click the settings icon and scroll to the bottom and there should be a import raw height map button, apply that to the terrain and scale as needed.