Hi there, there are nursing rooms all over the airport. Depending on which terminal you will be at, there are 17 in Terminal 1, 5 in Terminal 2, 4 in North Satellite Concourse, 11 in Midfield Concourse and 2 in SkyPier. https://www.hongkongairport.com/eng/passenger/arrival/t1/airport-services-facilities/nursing-room.html
Yeah it's available everywhere. And it's pretty nice. I am a frequent flyer and Hk nursing room is a personal Favourite. :) has a nice armchair and a door that locks and sockets so u can plug in your pumps.