At first you have a look up on you registration slip which was provided you when authority captured your photo for NID card.
There you have a form number. Collect that.
Now go to the election commission website.
You will see as bellow:
Now enter your form number in first input area and enter your birthdate in second input area.
Now input the captcha code and submit/hit enter.
You will be shown your desired details.
Thank you