When I try to use the qr scanner to get magearna it says that I can't do it on this system. Is this because I have the standard 3ds? Please help as I want this Pokémon.
Hmm, well on my 2ds QR codes work. Maybe it's because you didn't beat the Elite Four, or possibly you are doing the QR code to the wrong continent.
Go here: https://pokemondb.net/pokebase/274814/how-do-you-get-magearna-in-pokemon-sun-and-moon
I asked the same question. You will get a very good answer if you click on the site given. There is even the Magearna QR code!