Copy of i140 approval notice


I have my i140 application approved and currently within 180 days period after approval. My employer is not ready to send a copy of i140 approval letter. As I want a copy of this approval notice, if I file a FOIA request to USCIS will my employer be notified of this or not?

Also, is receipt number of i140 application sufficient or I also need A number on the approval notice to change employers in the future?