I’m not sure this is the way you’re officially supposed to get them but it works.
If you are one of the magical ambassadors you can enter the 3DS eShop, click the Menu tab in the top left corner, then go to “Settings/Other” and then go to “Titles You’ve Downloaded”. There you should find all 10 ambassador games ready for “redownloading”. You are, of course, not actually “re”-downloading them, but it works regardless and just makes you download them normally. I tried it and it works just fine.
If you don’t know, these are the games you can get:
- Super Mario Bros.
- The Legend of Zelda
- Wrecking Crew
- NES Open Tournament Golf
- Donkey Kong Jr.
- Balloon Fight
- Ice Climber
- Zelda II: The Adventure of Link
- Mario & Yoshi
Some of these games are really cool, so just do yourself a favor and get downloading!