so this is a magearna pk7 file that was obtained from japanese QR code.
if you have a japanese 3ds, just scan the QR code with QR scanner in game. for non-japanese 3ds you can either use this pk7 or change your 3ds region.
it's obtained only after elite 4, Lv50 cherish ball. it has your own OT, ID and you can nickname it.
it can be picked up in game from a man standing in front antique shop in Hau'oli city
QR code used to get magearna is this one >>>> https://i.imgur.com/FKVPh9K.jpg
i believe it was posted on here the first.