I currently use JKSV to backup and restore my 3DS game saves, but when I look for other saves online, this one website provides saves, but they are in this format:

00040000000EC300.sav

How do I covert these into something that works with programs like JSKV? Something that would be extracted with it and put into a folder?

(e.g. "main" for Pokémon games)

 

it's possible to get them to work, As stated above you cant use them if you dont have a Gateway, but you could ask someone nicely who has a gateway to convert it for ya .