This is a Wild Area event held by Sword and Shield. This event does not host any Gigantamax Pokémon, though some of the Gourgeist are forced to be shiny.
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 would contain 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.