Your amount of work experience puts you at the "old" end of the spectrum relative to the rest of the applicant pool. That isn't an automatic deal breaker, but be aware that most of the top schools' entering students only have 4-5 years of work experience upon matriculation. So, you'll need a crystal clear reason re: why *now* is the time for you to enter business school, as opposed to 3-5 years ago.
In terms of the GMAT, if you're starting from scratch, I recommend aiming for those schools' mean GMAT scores (between 710 and 720). You don't NEED such a score to get in, but anything below 700 will start to give admissions officers one more reason to reject you, so assume that you'll need to put in the effort to get to 700.
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