How much does my degree worth?

I have a bachelor degree in Business Administration (International Business) I have a six sigma blackbelt certification and a strategic planning certification from harvard, plus a five year work experience. But the problem is when I go to a job interview I do not quiet know how much should I say when they ask me for my desired salary. I do not want to be underpaid nor I do not want to shoot a number that is too high. Any advice anyone? How much money someone in my situation should ask for?