If you are attempting to enforce a judgment in another state then you will need to obtain a sister state judgment in that state. Most likely, that state will require a certified copy of the judgment. That is an easy process. You merely go to the clerk's office, and they will do that for you for a small fee. Alternatively, if you are using an attorney service, they do that all the time and can do it for you.
THIS RESPONSE IS NOT LEGAL ADVICE. IT HAS BEEN PROVIDED FOR EDUCATION AND INFORMATION ONLY. Mr. Mann is licensed to practice in the State of California. There is no implied or actual attorney-client relationship arising from this educational exchange. Moreover, the facts provided by you were not sufficient to allow Mr. Mann to advise you specifically regarding what you should or should not do. You should speak with an attorney licensed in your state, to whom you have provided all the facts before you take steps that may impact your legal rights. Mr. Mann is under no obligation to answer subsequent emails or phone calls related to this matter, or to take any action whatsoever.
You do not certify" a judgment. The court clerk will certify a copy of the judgment, if you pay a fee. If you want to enforce the judgment in another state, you will need to follow the rules of that state. The rules in the other 49 states are, often, similar to the laws of California. You would need to file a legal action in the other state and prove that the California judgment is valid. The defendant may be able argue that California did not have proper jurisdiction. That would depend upon the facts. If the judgment that you obtained was a default judgment, entered in Small Claims Court, the defendant may have a good argument. I suggest that you consult an attorney in the state where the defendant's assets are located.