PKSM VS pkmn-chest

PKSM is a save manager for Gen 3-7 Pokemon games. (Gen 3 games can be installed to the 3DS's internal memory like Virtual Console games, but you can't use the normal multiplayer features.) You can use it to generate/modify/clone Pokemon, but you can also just use it like an offline version of Pokemon Bank. It lets you move Pokemon around freely between games, well beyond the scope of official tools. There's a wiki link somewhere on that Github page that'll do a better job of explaining the features than me.

Simplest, use PKSM to transfer Pokémon from your Gen 4 cart to a 3DS game, then transfer to Bank from that 3DS game (assuming you want to go to Switch games, if all you care about is getting them on the 3DS game you never even need to use Bank)

Click on this. how to download pksm

This is the way. A tip, you have to tell PKSM where the save file for the game is. You can do this in the PKSM options under "Extra Saves". https://github.com/FlagBrew/PKSM/wiki/Settings

fyi there's also PKSM which is basically PKHeX but on console.

I wouldn't recommend it, just to be safe. I would try with PKSM, an application developed by the same folks behind Checkpoint.

I assumed you're on DSi because you said "DS XL" and that isn't a thing so I figured DSi XL, if you're on a 3DS XL though you'll actually want to use PKSM, it's basically the same thing but a bit better as it runs in 3DS mode.

pkmn-chest can do that

If you mean linking a DS ROM with a GBA save file, there might be something that supports that but I'm afraid if there is I don't know what. You could use pkmn-chest for that if nothing else.

I don't generally recommend video guides, but there is a text guide on its wiki.

As an alternative, use something like pkmn-chest to manually move them: https://github.com/Universal-Team/pkmn-chest

You need to use a save tool such as pkmn-chest. You won't be able to use the native tool.

On a DS flashcart you can use Pokémon Chest to move pokemon between games and otherwise edit your save files. You can also trade between a flashcart and a real copy of a game but you need to use a second DS and the normal trading mechanism. On a 3DS you have access to PKSM that will let you edit legit cartridges saves as well.

You can place your gba save file somewhere on the sd card of the flascart and use this: https://github.com/Universal-Team/pkmn-chest To move your pokemon between games

You could use pkmn-chest to move it, when going from an older generation to a newer generation the transfers are done exactly the same as the official method so the Pokémon will stay legit and all.