[Rookie]

Alright my teacher went by really fast in class today, and he stated a problem. I wrote the problem down, but now that I'm working on the problem I seem to be stuck. I don't know if it is because I don't have all of the problem down, or Im doing it wrong.
The problem is this:

55mg of Pb(CO₃) is put in water. The molecular weight for the lead carbonate is 267.209 g/mol. The Ksp is 3.1 x 10 ^-11 . How much of the chemical is left undissolved?

- I first started this problem by finding the number of moles. I multiplied grams by the molecular weight, and it gave me 2.06 x 10^-4 mol. Now I would assume I need Liters to find the Molarity and be able to calculate the soluility from the Ksp. But is that really necessary? I mean, can I just use the number of moles instead? and also, I don't think I understand the question very well either. How will I know how many grams of my substance is left undissolved?

[AWK]

Volume of water (~ volume of solution) is needed