I didn't reseve my user ID after rejestraion please help me
If you are talking about any exam then the general case for your USER ID is usually the Application ID which you can get from your confirmation page.
Also for most of the cases the USER ID and application details are usually sent to your registered mobile number or your registered email. So you can check there.
If any of the two didn't match then go to the official website and find out the forget USER ID option. Put the necessary details required and hopefully you will be able to retrieve your User ID.
Feel free to ask if anything else you want to know.
I hope this answer helps. All the very best for your future endeavors!