Tu t'appelle comment what is this in English?

You would want to say Comment t'appelles-tu? and it means "What is your name?". The inversion of the "tu" and t'appelles" makes it a little more formal.

The formal version of this is "Comment vous appelez-vous?" which is the most common way of asking since you're most likely not going to know the person.

(Literally they both mean "what do you call yourself")