How to change a scene after killing enemies

I have 3 scenes i have created with unity. In my first scene after killing enemies they keep coming and won’t stop. I want to kill few enemies in the first scene “say 10” and second scene “say 20+” and so on. And after killing enemies in first scene, i want to go to the second scene until the last scene.
i need help with this.
thank you

Make a script called “SceneChanger”. Attach it to a game object or whatever.

In that script, put:

public int killLimit; // so you can set this in the inspector for each scene (10, 25, 40 , etc.)

also,

private int totalKills; // keep a running total

So whenever you kill an enemy you call a function in that script, call it, “AddKill()”, where you would increment totalKills.

Then put in the update function:

if (totalKills >= killLimit) Application.LoadLevel(Application.loadedLevel + 1);

using UnityEngine;

public class SceneChanger : MonoBehaviour
{
public int killLimit;
private int totalKills;
public in AddKill()

{
if(totalKills >= killLimit) Application.Loadlevel(Application.loadlevel +1);
}

}

should it be something like this? Do you use C# or Js.