Many of the applicants have issues with this question as they are very focused on the immediate next steps and looking 5 or 10 years ahead of often scary/ridiculous/impossible for many. I would say you are further along than most. The more specific you can be in your mind (not just making stuff up but being specific), the better.
There is going to be quite a bit of soul searching in bschool with an internship in hopefully the industry/area you want to specialize in, and bschools realize that you may not have it all nailed down perfectly but the more specific you an be with the goal and showing how MBA will help you achieve it, the better.
And to answer your question - you need to be as specific as you are comfortable with. This will show/come up in other essays and also in the interviews. Don't be surprised if people question you/ask you why - the adcom wants to see if you have thought this through and wants to see your character (are you picking an easy path, are you passionate, or altruistic, or....)
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