Neither. The National Benefits Center is located in Missouri. Your USCIS field office is in Boston. I am a little surprised you were not interviewed yet, the waiting period should be long over.
If you file the I-130/I-485 package concurrently, it is sent to the USCIS Chicago Lock Box facility and after initial processing, the case is then sent to the National Benefits Center located in Missouri. Once USCIS has completed processing your case, your immigration interview will be scheduled at your local USCIS field office.
Akanksha Kalra, Attorney at Law: 215-542-4905 or email@example.com Disclaimer: The information provided here is generalized and should not be relied upon as legal advice. This communication does not create an attorney-client relationship.