Here is a tip. Use a value
Tuple to store the dice rolls. You can define a roll of 2 dice like this
(int firstDice, int secondDice) roll=(0,0);
roll.firstDice = random.Next(1, 7);
You need to define a list to hold the value tuples and a suitable loop to roll the dice while you have not got the required values. As a check to see that your while condition is correct, the probability of no success after the second dice roll is 2/3*2/3=4/9. So the hit rate is 5/9=55% giving a average list size of 1.8.