Alien Number of a naturalized child

[Pupmom 24]

I am helping my parents file their N400. They got their Green card through my brother who became a citizen around 8-10 years back. 
 

The N400 application asks for the details of children including their A number. Unfortunately my brother cannot find his paperwork and surrendered his GC when he got his citizenship. Do we need to add the A number for him or can we say he does not have one since he is a USC now?

 

Any help is appreciated!

[SusieQQQ 11,586]

It should be on his naturalization certificate.

[Pupmom 24]

Awesome! Will ask him to Look there! Thank you! 

[HRQX 4,145]

2 hours ago, Pupmom said:

Awesome! Will ask him to Look there!

On the certificate it's called "USCIS Registration No."

[Pupmom 24]

Thanks HRQX. Bro ended up finding an electronic copy of his paperwork - couldn’t find his naturalization certificate! Go figure! 
 

Hope this comes in handy for someone else in a similar situation.