This is a Wild Area event held by Sword and Shield. It appears this event hosts a bunch of rabbit Pokémon, probably to celebrate Easter.
This event gives players a chance to encounter a guaranteed shiny Azumarill. This event also hosts an uncatchable Gigantamax Cinderace.
To import these files into your save, use PKHeX's block importing function. Our tutorial should guide you through it.
Our first post of this page contains some data relevant to the importing stage.
There's info and some common questions regarding Wild Area Events here.
To see other Wild Area Events, here.