You need one of these two things.
[*]A DS unit that will currently boot the flash cart.[*]A DS unit that allows cart swapping, and another flash cart that runs on it.
1 is not true with you, and 2 is not true with the 3DS (no cart swap).
I suppose if I had an issue I'd just ask my friends at Gamestop for a used DS I could borrow for like 10 seconds. The Gamestop 'people' are ok really. Just regular people with a crappy job. As 'employees' they're annoying but they have to be because of all the stupid shit the regional managers make them do. While I despise Gamestop as an organisation, the people working there are ok (though of course you end up with the occasional douche bag in any working place