HELP: Having a hard time switching enemy types

I have been following along with a class from Udemy so I am still very new at this. I have managed to continuously spawn enemies of one type. I am trying to get the BP to switch to a new type of enemy after so many of the first type have been killed. Then, I want to do that again for the second type of enemy to call in the boss. Below is my BP that should be working in order. Thanks for any help.