Items needed for emulation on DS

Hey, recently I just bought a used original bulky Nintendo DS. I want to
run downloaded DS games off a flashcard, as well as emulate other games from other systems. Mostly, I just need to know what I need to buy to do this. I know I can't just buy an SD card.

If it makes a difference, I have a v4 DS.

I just sort of need to be pointed in the right direction in this.

You need this - http://www.gameboy-advance.net/nintendo_ds/nds_flash_card.htm

It says that you cannot play DS roms from the flashcard. I have seen this done on an origional DS before, is it simply because of the version of DS I am using? Even if I can't play DS roms, however, I'm sure going to enjoy the limitless amounts of games I will be able to play on my DS.

Thanks,