Please evaluate the right answer of the given question

Question- You rolls a set of m dice. If there were exactly six ‘6's present then you stop, otherwise you reroll all m dice again until this happens (assume m >=6!). Let Y = m (X + 1) denote the total of number dice that were rolled until you stopped.

Part 1- Identify the name and parameters for X's distribution.

Part 2- Write an expression (in terms of m) for P(X = 4).

I need help to write an expression for given point.