Here is the link:
http://www.uscis.gov/graphics/formsfee/forms/files/I-131.pdf
The following is from Page on this homepage.
"If you filed at a USCIS service center to adjust yourstatus as a permanent resident, mail this application to that service center. The service center address isnoted on the USCIS or former INS receipt relatedto the filing of your adjustment application. You canalso obtain the service center address byvisiting the USCIS website at www.uscis.gov orcalling our National"