If they are wild ducks, then they are probably this year's hatch. They sometimes land in strange places when they are getting used to flying and finding their way around. (If they are migratory ducks, they might be resting on the way to somewhere.)
I suggest you let them leave of their own accord and not keep them penned in at all, or feed them. They will find their way to a pond by themselves and be fine. You cannot really domesticate already wild ducks, they will bring potentially harmful bacteria, parasites or disease to your chickens, and will not be friendly or happy being confined.
Why don't you contact your local animal rescue if you need some help or advice?
If you are not sure whether they might be domestic ducks that have escaped from somewhere, then post a pic and we can help you identify the breed.