How to trade pokemon from and iphone to a ds?

The game on my iphone is sapphire (no jailbroken) and the ds game is fire red

I don't know if you can, because I don't know of a link cable that connects those two. I don't even know if the DS recognizes anything from an iPhone, because it is not designed to.

Considering the fact that I assume you are using an emulator, I don't believe you can. If you are, you would have to find the correct cable for it. But I'm almost positive that it's impossible to do so, considering the fact that the DS recognizes information from the game chip, which is probably coded differently than how it is on an iPhone. But again, I'm not sure. It might be possible.

You can't