"Mesh doesn't have normals. Please create some for GI" How to solve this?

The models are imported from sketchup and I had previously baked it properly. Now when I start recalculating lightmaps this warning is shown “Mesh doesn’t have normals. Please create some for GI” (999+ warnings) and the baking continues. The scene is not getting lighted properly because of this error(kind of reflective white texture for everything). I don’t remember any changes being made to the project to create such an error.
I tried making changes in import settings by switching normals between ‘calculate’ and ‘import’. How to create/ recalculate normals and solve this issue?

open your model in a 3d Software (ex. Blender) and click recalculate normals.

How can I find the wrong mesh ? Console report only error, not the gameobject.