TerrainCollider.terrainData on custom mesh

Ok so i need to make a new heightmap and the following code, and then i can simply assign it as the terraincollider.terraindata?

 TerrainData terrainData = new TerrainData ();
 const int size = 513;
 terrainData.heightmapResolution = size;
 terrainData.size = new Vector3 (2000, 600, 2000);
  
 terrainData.heightmapResolution = 512;
 terrainData.baseMapResolution = 1024;
 terrainData.SetDetailResolution(1024,   terrainData.detailResolutionPerPatch);
  
 AssetDatabase.CreateAsset(terrainData, "Assets/New Terrain.asset");