Where actually is Into the Unknown?

Hey, sorry to be the newbie asking dumb questions, but I've tried pretty much everything else I can think of to look for this. I'm trying to GM a one-shot for some friends and we're all new to Starfinder. I've seen Into the Unknown recommended a lot as a beginner module. The problem is, I cannot find this module literally anywhere. I've scoured through the paizo store and gone to the second pages of several google searches, I cannot find anywhere to buy or download it. Someone please help...