Convert a Legacy Safari Extension to a Safari App Extension

I have a legacy Safari extension and I need this to be converted to a Safari App Extension. The Safari App Extension won't require any additional features. Just make sure that all of the current features are ported over. The extension itself is a simple add-on that adds a button to the Safari window. This button allows the user to easily change countries when looking at a Google Search result (for example, from [login to view URL] to [login to view URL]). The extension also allows the user to modify some options (e.g. add or remove countries, reorder how they appear in the country list, etc). I will provide the code for the current legacy Safari extension. I also have the same extension for Chrome, which I can provide if needed. Here's some documentation from Apple on this type of conversions: [login to view URL]