so, I got the new Pokemon mystery dungeon game on the 4th knowing about the event theme, but I can't figure out how to get the theme now. it said on the download that there should be some sort of code that gets the theme but I can't find it
The code is on your eshop reciept. If you don't know how to view that...
Go to the Nintendo eShop app.
Scroll down and select Settings/Other
Scroll down and select Account Activity
You'll see the game somewhere here. Click on View Reciept, and the code will be somewhere in there.