How to prepare phosphate buffers of different pH values?

Please, I need help to prepare different phosphate buffers of pH: 3, 5, 7, 8 & 9 with KH2PO4 & K2HPO4. I am going to use these buffers for enzyme stability test. I need to know what amount of each chemical should I use and if I have to use extra chemicals such as NaOH to get the required pH.