No offense, but you have repeatedly asked about eggs and baby ducks. I'm guessing that since you did not originally Know the kind of duck, and do not have the appropriate equipment for Raising said ducks... these ducks are probably not Domestic Mallards.
It's fine, I really don't care as long as it doesn't turn into a "I want the pretty birdy, oops they died" moment. But the care for a domestic mallard will be different from the care for a wild mallard. Wild mallards need to migrate for survival. Since they're hatching Now, I'm guessing you live in the middle states. If you were North they'd be hatching next month, and if you were south, they'd have already hatched. That means you have cold winters, and I'm betting you don't want to build them a heated shelter or chip their little feet out of the ice all winter.
So, if they're not domestic mallards, you'd be raising them for release. And they'd have to be released near a natural flock well before fall. Till then, go to a feed store and get either duck food or wild game bird food. They'll need lots of water as well. They'll need heat till they are fully feathered.
It's a good idea to take them outside once they are a week or so old so that they can pick at grass and bugs and start some natural behaviors. Don't let them swim in any pool that is treated. They can, however, spend some swim time in a kiddy pool if you watch them closely. Down isn't as waterproof as feathers and they can get tired and waterlogged.
Best of luck.