Breastfeeding in the workplace laws

Does anyone have any insight on pumping at work? I did a brief google search and it looks like I’m legally required in the US to be given adequate time to pump (which for me is at least every 3 hours). How do I go about bringing this up before I go back to work next month? Has anyone had to do this? I’m a nurse and it’s never even known when my lunch break will be so I don’t know how getting extra pump breaks is supposed to go. But I’m exclusively pumping and my supply will take a huge hit if I’m only able to pump once on my lunch break at work. Help please!