Where to find affidavit number in my affidavit?

It's a serial number which is always mentioned at the side of notary signature or it  can be on the stamp paper like below mentioned in photograph.

As per the notary  rule, it is mandatory for the Notary public to maintain the notary register and enter the serial number on the said Affidavit or any other notarized documents. 

              In notary register he must enter the details of party/parties/ witness/witnesses with their signatures.