Hello Rohit, I request you to please help me with the portal of which you've forgot the user I'd so that I can check and provide you the exact information about how you can recover it yourself. Usually at the time of registration portal ask you to submit your email address and the second you make your account it send a computer generated message on your registered email address with your user I'd. You can search in your mail box also check in archive or spam folder.

Feel free to comment if you have any doubt

Good luck