That seems like a set of instructions or a sort of game plan. A better English sentence would be "When we are done drinking, you will pay".
Neither are a correct translation of the German sentence, though, which doesn't have a "when" and only says "trinken". Usually, the simplest answers are best.
I was taught that "zahlen" was to pay, and I understand all of the conjugations of the word (I got the question correct), I am just not understanding how we go from "zahlen" to "bezahlen". Where does the "be-" come from? Is is saying "you will be paying" and that is why the "be-" is there?
You generally can use either zahlen or bezahlen to say to pay. There is still a subtle difference:
Ich zahle Steuern.: I pay taxes. For this general statement you use zahlen. Bezahlen is more the act of paying itself. Hopefully you're not the one paying generally in the pub ;-)