I'm not sure on the exact methods but I do know you can use a certain variety of Action Replay for the Gameboy Color, but it requires a old computer with a parallel port (the long pink connector) and some old software. Also I'm pretty sure the Gameboy Action Replay is pretty rare and expensive but I may be wrong.
Also it depends on the region of your Pokemon Yellow cartridge, for example if you've been playing on the American version of Yellow on an Emulator but own a European Cartridge of Yellow then I'm pretty sure you're out of luck.
There are videos on Youtube explaining how exactly.
Most emulators that I've messed with generate a .sav file for the game save data. You could get a cartridge reader/writer device and transfer the file to the cartridge. These devices run around $50. I've had good luck with the one from BennVenn: https://bennvenn.myshopify.com/products/reader-writer-gen2
Same concept would apply if you use something like the Everdrive, but you wouldn't need the cartridge reader/writer. You would just transfer your file to the sd card you put into the Everdrive.