Hello

First, check your admit card, registration form, or previous mark sheets  it’s usually printed there.
If you can’t find it, visit your training institute or college; they keep student records.
You can also check the official website of your state’s education board (e.g., BSEB for Bihar). Many boards offer a “Forgot Enrollment No.” or “Student Search” option online. You may need to enter your name, father’s name, DOB, and exam year. If online recovery fails, contact the board’s helpdesk or visit the office in person with ID proof.