Light Baking Issue

Before I have real-time lighting because of the performance issue, I decided to do light baking for my 3d game. So I have mark 3d environment as static because it remains on screen always without movement.

Also changed direction light mode to Mixed because I have few moving game objects too.
But after the baking process gets completed, I got this kind of output:

In above, you can see in the above image what happened with my environment after baking.
In the above image, I have also included light settings if you need it.

You have to enable lightmap UVs in your 3d imported model file.

I got this reply from one forum member so exact wording, I am posting here: