I had no idea this event was going on until today. There is still time to pick up a code from GameStop if you haven't already. The event will last from May the 4th to May the 27th.
https://www.gamespot.com/articles/pokemon-free-legendary-available-now-for-ultra-sun/1100-6458735/
https://www.gamespot.com/articles/pokemon-free-legendary-available-now-for-ultra-sun/1100-6458735/
