I don't know about which examination you are talking about. You can get the hall ticket number from the hall ticket or the admit card. Now if you don't get the hall ticket then you have to wait for some time until and unless the Hall ticket or the admit card releases.

In the admit card there you get the venue of the examination, date and time of examination and the admit card number. So you will get the number from it only.

If you want to know about a specific answer, I would recommend you to repost your question with proper question specifics (name of the examination about which you want the hall ticket number) so that we can provide you all the information about it.

Have a great day!