What should a young professional be asking for in terms of salary range?

Here’s the background:
BA in Biology
MPH in International Public Health
CPH (certification in public health)

applying for my first full time position, have lots of prior experience but it was rarely paid for, employers want to know what my salary requirements are and I am not quite sure what to put…careers in public health are wide ranging and one can work for $30000 or $70000+...I dont’ want to ask for too much or too little…what do you think…