Make imported 3D model behave as Unity Terrain

Hi!

I have a model of a terrain with assets properly placed and ready to be imported in the game. This model was created in your typical 3D software editor and exported all in different objects and properly laid out. Not having constructed the terrain within Unity’s Terrain editor, Trees and Mesh Details are already placed. How would I make those assets behave like trees and detailed grass, because I want them to react to wind, or sway gently.

For instance, would replacing the shader of the trees I want to be able to move, to a shader that the Unity Terrain Editor uses work? Same for detailed mesh.

Thank you.

For those who might bump into this.
here is a possible solution. Vegetation animation on non-terrain mesh? [YES] - Questions & Answers - Unity Discussions