Quick question. How do i get an object to come down once all AIs are destroyes and then when i come near it it loads a level

Well, The title says it all.

Well, you could do something like this-

Put a big trigger volume on the object, and then make a script for counting the number of enemies in the scene-

float heightProportion = 1;
public Vector3 someHighPlace;
public Vector3 someLowPlace;

Update()
{
    if(GameObject.FindGameObjectsWithTag ("Enemies").Length == 0)
    {
        heightProportion = Mathf.Clamp01(heightProportion - Time.deltaTime);
    }

    transform.position = Vector3.Lerp(someLowPlace, someHighPlace, heightProportion);
}

This will move your object when you run out of things to kill.

Then on your object, do something like this-

OnTriggerEnter(Collider other)
{
    if(other.gameObject.tag == "Player")
    {
        Application.LoadLevel("Next Level");
    }
}

This is all strictly psuedocode- while it’ll techincally compile in C#, you’ll have to adapt it to do exactly what you need it to do. Most notably, you need your enemies to all share a tag, and you need your player to have a different tag.