I am using Unity and I developing an app for iOS. How do I implement in-app purchases that work world-wide?
Apple provides a framework for in-app purchasing in StoreKit. You can read the docs on it here. From their documentation:
How to implement in-app purchasing is more involved than the format here permits, but the general areas that you're going to need to learn about are:
Here are some additional resources you may want to look at: