How do you get Coin Case in pokemon LeafGreen?

You can't actually get a "Coin Case" item in Pokémon LeafGreen. The closest equivalent is the "Save Case" item, which increases the number of save slots you have available.

Here's how to get the Save Case:

1. Defeat the Elite Four and become the Pokémon League Champion.

2. Speak to Professor Oak in Pallet Town. He'll give you the Save Case, allowing you to save more than one game on your Game Boy Advance.

While there's no Coin Case in LeafGreen, you can still collect coins in the game. However, their main purpose is to buy items at the game corner, which is a mini-casino in the game.

Let me know if you have any other questions about Pokémon LeafGreen!