How to get US marriage certificate certified for acceptance for Kor Ror 22

[Equatorial]

I am trying to get my Kor Ror 22 for my marriage-based Non O. I have the original marriage certificate (from California) from 2010. The local Ampur insists that my wife submit a certified certificate along with the translation. I check the US Embassy web site, and it states that they don't certify state documents, and they don't certify affidavits any longer. 

 

What is it exactly that I need, and what is the procedure to get it. (If this has been answered, please point me to the right post; I searched but didn't find the answer...)