Usually you will find the ticket number printed in the first line of the skipass. It is composed of 2 numbers separated by a / (do not enter the / character!).
On this picture you can see the 2 numbers within the blue frame. In this example it would be:
102 18806
Usually you will find the ticket number printed below your name. It usually contains 8 digits or letters (A-Z).
On this picture you can see the skipass number within the blue frame. In this example it would be:
91642912