For those wanting to stay safe:
If your console is connected to the internet, it should download automatically. You can also manually trigger it by pressing the on the game icon and selecting Software Update Via the Internet Expansion Pass (DLC) Details Splatoon 3: Expansion Pass is a paid bundle consisting of two main waves: Wave 1: Inkopolis Revisit Inkopolis Plaza from the original game as an alternate hub world.
Leo stared at his Switch, the neon screen flickering as he scoured the deepest corners of the "Ink-Net." He wasn't looking for a standard match; he was hunting for the —the legendary Splatoon 3 NSP file bundled with every update and the Side Order DLC [1, 2].