They'll probably ask you what drives you to go back to school, what your career goals are, and what makes the school a good fit for you (or what makes you a good fit for the school). They may ask about specific experiences that have shaped your decision to go back to school. Good luck!
When I interviewed with Johns Hopkins, they asked why I wanted to go into the specialty I chose. How much clinical experience I had in health care, and what makes me motivated to do an accelerated masters degree in nursing.