Please use code tags: Using code tags properly
The best way to spawn things in a pre-made level is to put GameObjects (invisible with nothing on them) where you want the spawn to happen, then drag that gameObject into your script to use as a position.
You can also add gizmos to these invisible gameObjects so they show up in scene when you’re working and editing your level, or even write your own custom gizmos with OnDrawGizmos() or OnDrawGizmosSelected().