I am working on a virtual lab for chem 123 at UBC and need help on determining how many ml of NaH 2 PO 4 needed to make a buffer solution. I am given...

I am working on a virtual lab for chem 123 at UBC and need help on determining how many ml of NaH2PO4 needed to make a buffer solution. I am given that the molarity of the stock solution of H2PO4- is 0.50 M and NaOH is 1.0 M needed to prepare 100 ml phosphate bugger.

I do not know where to start.