DS games on 3ds ?

im trying to download zelda games for ds on my 3ds , but did not find it on eshop , why ?

and can i use DS game card on 3ds ?

There's only a few Zelda games on the eshop (all the GBC ones if I'm not mistaken). And yes you should be able to use any ad all DS game cards on the 3DS.

There are no DS games on the 3DS eShop currently. Sorry.

All DS cartridges work on the 3DS though.