UnityEngine.Object[] prefabs = Resources.LoadAll("Terrains");

        for (int i = 0; i < prefabs.Length; i++ )
        {
            Debug.Log(prefabs[i].GetType());
            prefabs[i] = Instantiate(prefabs[i]);
            prefabs[i] = GameObject.CreatePrimitive(PrimitiveType.Cube);
            Debug.Log(prefabs[i].GetType());
        }

        foreach (GameObject prefab in prefabs)
        {
            prefab.transform.parent = prefab.transform;
        }