(deleted, see next reply)

You can find the install location of a specific extension in the extensions.json file in the profile folder.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

You can open the extensions.json file in a Firefox tab and search for this extension. The path field lists its install location.

• https://developer.mozilla.org/en-US/docs/Tools/JSON_viewer

Note that Firefox no longer allows external software to install extensions in Firefox by Sideloading add-ons via the Windows Registry, so you would have to install the extension yourself via the Add-ons website or allow the website to install their extension via "Tools -> Page Info -> Permissions" if Firefox doesn't ask for permission.

• https://support.mozilla.org/en-US/kb/find-and-install-add-ons-add-features-to-firefox