From what I've read about breeding Sun Conures, three eggs is about right for a clutch size. If she has been incubating full time (sitting on the eggs most of the time with short breaks to poop, stretch and eat) they should begin to hatch after about 21 days (from start of "full-time" incubation). The eggs should hatch in the order they were laid about 24 hours apart. As you see, there are lots of "should" here! First, the eggs need to be fertile. If you remove the eggs one at a time and set each one carefully on your cell phone flashlight you will be able to tell right away whether they're fertile. At about 7-10 days incubation you will be able to see a dark red mass with lots of red blood vessels branching out through the large yolk. You may be able to see the red mass rapidly pulsate- it's the chicks heart! As incubation and development progress, the inside of the egg will be taken up more and more by a very dark mass which is the baby bird. By the end of incubation, very little light will pass around the chick which almost fills the egg except for the air sac at one end. I believe the hen can feel the chicks moving inside the eggs toward the end of incubation and right before they hatch she can hear them peeping inside the eggs.
I would check the eggs now to see if they're fertile. If they are, just sit back and wait for them to start hatching. If they are not fertile, the female will start losing interest in them around a week after they should have hatched and you can then dispose of the eggs without upsetting her.