This is a Wild Area event held by Sword and Shield. This event does not appear to host any Gigantamaxes.
This appears to be the default max event raids that Sword and Shield will use going forward (ignoring the monthly 1 week events).
This "monthly default" went into use starting April 2021.
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.