If your green card has not arrived yet, you can request a new green card from U.S. Citizenship and Immigration Services (USCIS). To request a new green card, you need to file Form I-90 to USCIS. Before you apply Form I-90, however, make sure that at least 30 days have passed since USCIS mailed you the green card. It typically takes up to a month to deliver your green card back to USCIS if it was not delivered to you.
You may also need to check with the local post office if they have a mail that you did not receive. If you have registered an online account with USCIS, you can sign in to your account to see if your green card was transferred back to USCIS.