How do I trade from pokemon ruby to diamond?

how do I trade from pokemon ruby to pokemon like if I wanted to get the regi's from ruby and trade them to diamond to get regigagis

alright dude first you have to see all 150 pokemon and beat the elite four.. then you go and talk to Prof. Oak at route 212 I think its the migration thing at the sart up screen.. then all you have to do once there migrated is catch them at the ' migration' building' or whate=ver its called.. dont worry you catch all of them 100 % of the time so your good even with the legendaries!!
Hope That Helps!!

this is also inside your manual but if you dont have it here you go.

once you get the national dex and beat the elite 4 , you then unlock a place called pal park. once you unlock pal park , you can put your ruby in the second ds slot. at the start of the game where it says new game and continue game it should now say ' migrate from..' select this and it will allow you to pick pokemon from your pc on ruby to migrate up. then go to the guy in the pal park place at the end of the route at the very bottom of your map. he will take you inside the building and allow you to catch any pokemon you migrated.inside this miny park. the pokeball will automatically catch them. dont worry about the level.you can do this with 6 pokemon once every 24 hours.

What I did:

Beat the Elite 4, and see all 150 Pokemon for your Pokedex. Then on the first page where you would select 'continue' or 'new game' there will be a new option 'Migrate Pokemon from Fire Red' or whichever GBA version you have in the slot. It will then ask you to choose 6 Pokemon to import from the PC on your GBA version. It will save it on both versions.

Except, I did this and am not sure where the Pokemon I transfered were placed. They don't seem to be in any of the boxes on my PC. So a little help would be nice.

So where is the Pal Park?

to get national pokedex do I have to catch all on leafgreen then trade all to ruby or do it once and it automaticaly open the slots for me to go and try and catch

When can I trad in pokemon ruby to another ruby

to reach the pal park you have to surf down and then right from the beach at sandgem town

once you get the national dex(after you complete the sinnoh dex) you will be able to 'migrate' from your previous GBA games