。
You don't know what it's like to be poor.
Literal
Poor [quotative-と] [called-いう] thing [subject-が] what kind-of thing [copula-なの] [topic-か] you [topic-は] do-not-know.
The embedded question どんなことなのか ('what kind of thing it is') is the object of 知らない. ということ nominalizes the concept of 'being poor.' A rebuke suggesting the listener lacks the experience to understand poverty.