Use this question as an opportunity to highlight past success, and explain how your career has grown so far. This will allow you to explain why you want this role to be the next step in your career.

"I've spent the last few years working as an associate at ABC Firm. In that role, I have learned how to counsel clients through various issues, focusing on mergers and acquisitions. I have found that I enjoy thinking through the effects these deals have on businesses. After talking with colleagues who work as general counsel, my understanding is that they do this daily in the work they do. I want to transition into an assistant general counsel position so I can focus on one client and use my business skills to ensure the company is protected and in the best position to meet its goals in the coming years."