In which file are stored an add-on settings/options?

Lest’s go inside the FF user profile’s folder:

In which file are stored an add-on settings/options? How to find the file storing a specific add-on?

Like this one:
https://addons.mozilla.org/en-US/firefox/addon/easy-google-translate/

Thanks in advance and regards

It depends on how the extension is designed and which storage API is used.
If it is a WebExtension and it uses storage.local, then the settings is stored in Profile Folder/profile.name/browser-extension-data/{extensionid}/storage.js
However, an extension can also use storage.sync which stores the settings in the cloud for example, and unfortunately you can’t have access to it.

or any of the DOM storage APIs etc. It would really help to state your intent, too.