So, I'm Stuck

Hi everybody! Just as an experiment, I am attempting to transfer data from my ROM copy of Pok?mon Pearl to my physical copy of Pok?mon Pearl, but I don't even know where to start with it. I am unsure of how I would transfer the data from my physical copy of the game to my ROM copy so I could do what I needed to do before transferring it back to the physical copy, so could I get a bit of advice? If I succeed, I plan to transfer the Pok?mon from the physical copy to the ROM copy, and see if it would be possible to modify them at all, before returning them back to the physical copy. I also intend to attempt manual duplication, simply by copying whatever file the data of an individual Pok?mon resides in. So, may I get pointed in the right direction with this?