Change Level in Game

Unity Engine
1

I have completed my game. However, how do I change to the next level? For instance, I want to kill 30 enemies and then go to the next level. I know I have to use var enemyPrefab : GameObject; to add my enemy to the script. However, what will I use in the update function?

2

@popmog78
Check out the application command.
-S

3 
if(????){
	Application.LoadLevel(?);	
}

Replace ??? with code and ? with level number (you can find this under build settings)