EnemyMakerRandom.js

var prefabAsteroid : Transform;

function Start () {
    for(var y = 3; y < 4; y++){
        for(var x = -3; x < 4; x++){
            var prefab = Instantiate(prefabAsteroid, Vector3(Random.Range(-5,5), Random.Range(-5,5),0), transform.rotation);
        }
    }
}