None of these are natural.
Probably you want something like
How many more times do I have to tell you [to sit down]?
You use "many" because you are asking for a counting number. The word "times" is countable. "How many times" is a common phrase. I've used "have to" as this is less formal than "must".
This is a rhetorical question. You don't want your friend to tell you the answer "You have to tell me three more times."
There are other things you could say.
How many times have I told you [to sit down]?
Do I have to tell you again?
I'm not going to tell you again.
This suggests that next time you will take action!
It is always going to be a bit rude to talk to someone like this. Whether this is okay depends on your relationship. It might be hard for a language learner to judge rudeness.