If you are studying any course from a college, then you must have a registration certificate which is essentially a certification provided that you have registered under the university. Now due to any reasons if you won't get the certificate then I would recommend you to go for the hall ticket you have been provided for the examination, you will get the registration number there as well. Now if you don't get that then I would recommend you to contact your Departmental Head or the college authority who can provide you the details.

I hope this answer helps. All the very best for your future endeavors!