Just a quick question, How do you get your original games on the memory card to play and what is there average file sz?
Theres no real way to rip roms from your DS cartridges. You have to find and download the roms from the internet. As for filesize, they come in several sizes: 8mb, 16mb, 32mb, 64mb or 128mb. Most are either is either 32 or 64mb.
For obvious reasons I cant give you direct links to download them. But Googling "NDS rom download" would be a good place to start. If you know how to use bittorrent then piratebay or mininova are always options as well.