Girls, help me, I have no strength left. When did you get your milk? I…

Girls, help me, I have no strength left. When did you get your milk? It's been three days and there is none. The baby isn't getting enough from breastmilk, so I had to switch to formula feeding. She won't sleep and cries, and I can't do anything but give her an empty breast. She keeps crying and I cry too. What can I do to make milk appear at the breast from birth? I'm attaching her often.