Expect it to arrive in 2 to 4 weeks after your application reaches USCIS.
Then the appointment is likely to be 1 to 3 weeks after you get the notice, but you once you have the notice in your hand you can go for a walk-in before the appointment date.
EB3 ROW I-485 Approved: July 2007
USC: July 2013
I am a layman, not a lawyer. What I write here is not official or professional legal advice. In addition, my answers on this forum are specific to the scenarios discussed in each thread and should not be generalized to other situations.