Translation:We want knives and forks.
Of course, and as usual, the acceptable English answers are zilch. What is wrong with: "We all want a knife and fork". It won't accept it though.
Yao 要 can mean anything from want, to need, or have to have something. And 我们 can mean we, we all, or we both. The rules change all the time in this course. Drives you nuts, other courses like the French course are very slick and good products but the Chinese never seems to get any upgrades or work done on it.
It doesn't need to be plural. Although in most contexts that you'd use this sentence it probably would be. Regardless, duolingo wouldn't accept the exact sentence you wrote anyway since English needs articles, i.e. "We need a knife and a fork". I don't know if that's accepted because I haven't tried it, but it should.