Translation:It is going to be necessary to put away the dishes that have dried.
This is because English typically uses “we” or “you” instead of “it” when referring to these kinds of necessities. The English only sounds clumsy because itʼs being translated from a language where they prefer to use the dummy subject “it” to refer to general necessities like this. You will see a lot more English being translated from French that sounds and feels really weird since Duolingo tries to have you give the most accurate translation that English can offer. This is why being a translator for subtitles and other things is so hard: you have to be able to take something like this French sentence and translate it into something that is not only natural to speakers of English (or whichever language youʼre translating into), but also as accurate as possible to the original language being translated from.
For most verbs, avoir is the auxiliary verb used to form the passé composé tense. This tense has already been extensively studied. If you don't understand it, it would be worthwhile to go back and study it more.
There is an adjective that means dry -- sec or seche. But the passé composé verb is what's being used here.