DO A BAR-
Are talking about the platformer tutorial?
Anyways, you can use the global variables for the system to know when you killed all the monsters. Let's say there are 9 monsters.We'll call the variable "enemies killed".
You can use the "When destroyed" thing to check if the monster is dead. Then, you are going to use this:
System-> Add to global variable
The full event will look like this:
Enemy:When Destroyed-->Add 1 to global variable "enemies killed"
Now, we need to add the event that will jump you to the layout when "enemies killed" is equal to 9. That, of course, is what you can do.