How do you trade between diamond LeafGreen?

Answer 1

It's not possible to trade between Diamond version and Leafgreen version instead a feature called Migrating was introduced in Diamond utilizing the GBA slot in the DS console. Put Leafgreen in this slot and turn on Diamond and press start on the title screen and you should see an option called Migrate from Leafgreen. Press A on this option and follow the onscreen instructions in order to migrate. It's important to save both games in a pokemon center as well as have the pokemon you want to migrate in the PC rather than in the current party. One last very important note:You must obtain the National Dex in both games as well as give the Ruby and Sapphire items to Celio in Leafgreen. To get the pokemon you migrated go to the Pal Park in Diamond and you will be given Master Balls to capture the migrated pokemon. Run in the grass and water to find all your pokemon (only water pokemon will appear on water and some require a fishing rod to be used). After capturing them they will appear in the PC. Remember that only 6 pokemon can be migrated at a time and pokemon with HM moves cannot be migrated so make sure to remove these moves and lastly migrating can only occur once a day (if you change your DS time you can migrate whenever).