There is no real-world "Game Show Island" with a universal code. You're likely referring to:
Poptropica's "Game Show Island" (2011) — a quest island. Codes are puzzle solutions (e.g., trivia answers, pattern sequences) unique to each playthrough.
Roblox / Fortnite Creative map named "Game Show Island" — creator sets custom codes.
Board game / TV show tie-in with a code card.
How to Find the Code
Identify the exact game/platform.
Search "Game Name Game Show Island code" or "walkthrough".