Create List of PopupMenuItems from firebase data

Question

I have 3 cars docs in the Cars collection in my firebase cloudstore. I want to create a list of PopupMenuItems in my PopupMenuButon based on the number of cars in my Cars Collection. I also want the value of my PopupMenuItems to be the names of the cars in my Cars collection.I need help because I'm stuck and I don't know how to go about it.