Hi hope you are doing good.

your question is a bit confusing but I think you are asking about where you would get your registration number and application number.

I don't know whether you had applied for JEE on neet or any other exam but every national or state level exam communicates with the candidates through two ways.

1. Mobile phone number SMS

2. Email.

I hope you remember the email id you registered with. If you have that email you can go to the inbox and search for the mail from the official authority of the exam you applied to.

Also in the mobile number you will get information about the exam.

most likely you will receive the registration number or your application number on your mobile phone or your mail.

Then you can login to the official website of that exam you applied to.

Enter the registered mobile number aur email and click on forget password they will send you a verification code and you will be able to reset your password. after that just reset your password and login and you will be able to see an application form.

most likely on the right side upper and follow you will find the application number. the entire application would have your name your father's name your mother's name your address your education qualification and many other things you can edit the things you want to.

Note down this application number as you will need this in future.

Also keep a note of the registered email id and phone number and also the registration number and password.

if you have any problem you can just comment below in this answer I will try to help you as much as I can.