For this question, you should give specific details about your profession first and then about the level you hope to achieve within 3 and then 5 years. The hint is don't aim too high, as the interviewer may be afraid that you will get his/her job soon.
"I have given a lot of thoughts about my career development, and from that process I have developed a plan for achieving my long-term objectives such as .....(being an expert in ..., or becoming a project manager... etc..) . And I see that this position is an important step in my long-term plan.