What do I do with green card?

“Once you receive the green card from the Post Office, you need to check that the card has been signed and then you need to create an AFFIDAVIT OF SERVICE by Certified Mail to file in the
court file.”

So, once I receive the green card back, I need to take it and the affidavit of service back to the courthouse? Can I do this before the 30 days or does that happen when I request the court date?

You can do it at any time prior to the hearing on your divorce. You should bring a copy of all your filings with you to your divorce hearing, but especially make sure to have a copy of the affidavit if you filed it close in relation to the hearing date. There is always a possibility that it could be filed and not yet located in the file on the court date.