This is a Wild Area event held by Sword and Shield. With this event, you get a chance to encounter Giganantamax Venusaur; and with 5-stars raids, you get a chance to land on a 2% guaranteed Shiny Politoed slot. The theme of this raid focuses on frogs.
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.