Yes to go online it needs a proper header and the .3dz file extension. I wouldn't use .3dz though, as even people using private headers have received that #banhammer, while there have been no confirmed cases of people getting banned using .cia versions. TL;DR - 3dz bad, cia good. Convert your roms.
i don't need to go online i need only the local 3ds wireless communication for local play without internet that is allowed with 3ds format?
If it doesn't require you to to connect to nintendo network then I think you can use just the .3ds version. But I could be wrong.
In order to trade locally you have to connect to the nintendo network, they will need to be .3dz with a working header or .cia in order to this.
is not needed the nintendo network i assure u i have traded from x to y retail games in a place without internet; anyway thanks for the answer ^^
