cannot find *.nds file in GBAMP game folder

Hello everyone, would really appreciatde any help you could give me. I'm new to the whole DS thing but found out about an adpter enabling me to play movies games etc so i opted for this instead of the psp.

i bought the mariokart game pack serial no: NEH 1190......
and a

GBA Movieplayer M3 adapter (M3 perfect) which stung at £78!

it also comes with a little device known as a passkeyDS. I'm having a couple of problems. I've been able to convert an mp3 file ok, ive converted 1 movie file but it doesnt play full screen on GBAMP and sound is shit! also ive downloaded a load of DS roms from a torrent site *.nds and assumed i could just copy these onto the SD card. but when i go to look them up on the gbamp in game folder there is nothing there. ive even tried to convert these files on the m3 game manager. Could anyone please help me. Ive heard of flashme or something so i dont have to keep using the crappy GBA catridge slot, am i right? also what does this passkey seem to actually do as i can access the gba and play movies and music without it inserted. and what is the passkey/card button for on the back, it doesnt seem to tell people about these things anywhere!

thanks in advance guys

Since you downloaded .nds files from bittorrent, I have no choice but to assume that they're warez.

Just as a note, nobody's going to help you with warez, since its against the rules here.