Nintendo DS; Slightly Confused

So, I'm rather new to the whole downloading NDS ROMs, and I've successfully managed to download them.
However, my problem is that whenever I try to play them, it tells me that the card is unavailable or something along those lines (well, the Japanese/Korean ones that I downloaded). I'm assuming the ones that were made for America are also similar?Could someone explain to me the problem? Thank you!

First make sure you extract them.
https://www.romulation.org/forum/index.php?topic=3880.0Then, you need to tell us what card you are using, R4, R4i, Acekard, M3, etc.

Okay. Thank you for the information!