hi,

I assume you are asking about the entrance test cet number in which you have registered , however every year numerous number of candidates enrolled for different entrance test and once the exam and counselling over the data is removed from the website, if old website is available you may check if any thing found or not , or you may check the email id of which you have entered for form filling.

another  option is contact with college, since at the time of admission you must have submit the documents in which cet number may have mentioned.

hope it would help.