Part 3, Question 1 on Form I-90, Application to Replace Permanent Resident Card, asks about the "location where you applied for an immigrant visa or adjustment of status." In other words, they want to know where you applied for your green card.
First, you must determine if you used consular processing or adjustment of status to obtain your green card.
Adjustment of Status
If you filed an Application to Register Permanent Residence or Adjust Status (Form I-485) because you were already in the United States, the location will be the "City, State" of the USCIS office where you filed. Usually this is the service center that you mailed your application. You may need to review your original paperwork if available.
The location where your adjustment of status was granted is the USCIS office that granted or denied your application. You can find this information on your green card. More help here.
If you filed for an immigrant visa through consular processing, the location will be the "City, Country" of the U.S. Embassy or consulate where you originally applied for your visa.
If you entered the U.S. with an immigrant visa (consular processing), be sure to complete questions 3.a. and 3.a1. For 3.a., your destination is the U.S. state that you initially settled. For example, if you entered the U.S. in Nogales, Arizona, but you were on your way to stay with family in Denver, Colorado, your destination was "Denver, Colorado."
For 3.a1, your port of entry was "Nogales, Arizona" using the example above. For additional step-by-step guidance on these I-90 questions, try CitizenPath's online I-90 preparation service.