Why dont you google it? TWLoader can load some roms, and many flashcarts work on luma. Seriously...
Well, obviously OP is not that a knowledgeable person as
@Zabhahs is and that is no problem at all!
I'd like just to say that I specifically googled "convert ds to cia" like
@Zabhahs told OP. That resulted in sites where it was discussed that this was not possible (at that moment). One source on the first page has "TWLoader" in its title but the page's name (wololo) sounds quite strange. There would be the solution, yes.
But actually, OP asked for conversion.
@Zabhahs gave a possible solution without the need for conversion. What I want to say is think yourself into OP's position. He might never have heard of TWLoader (unlike
@Zabhahs ) which is no problem but make sure you write it in a (more) polite / constructive way.
If I were OP, the probability of me posting another thread with a concerning question would be lowered by answers like
@Zabhahs'.
I am not trying to defend OP like police but I know we all were beginners in CFW. And even if we got CFW, does not mean we understand it or all of the open possibilities. There is no dumb question, only mean answers.
I am also not trying to attack
@Zabhahs! This just bothered me.