When you are filling out your Form I-90 application to request a new green card, you may need to write or type the Port-of-Entry location where you were admitted in the United States. Fill out the field 3.a.1 with your Port-of-Entry only if you arrived in the U.S. with an immigrant visa.
Put simply, a port of entry is any government facility where aliens or U.S. citizens arrive in the U.S. Such facilities as airports and border entry points are typical examples of ports of entry. Write the city and state of the airport or border point where you were admitted into the Port-of-Entry field on Form I-90.