Finding the Safari settings (default search engine in particular) are stored

Recently, my default search engine changed (from Google to Yahoo) on Firefox, Google Chrome and Safari. I could easily changed the settings on Chrome and Firefox but for some reason it doesn't work with Safari.

In the Safari settings, I can change the default search engine to Google but it has no effect and Yahoo is always used. The issue has already been describe (but remained unsolved) here.

I tried going to my safari folder to find out where this information is stored but I don't really know what to look for. I have two folders named Safari:

Macintosh HD ▸ Users ▸ myname ▸ Library ▸ Caches ▸ Metadata ▸ Safari

Macintosh HD ▸ Users ▸ myname ▸ Library ▸ Safari

Do you know where I can find the file where the default search engine for Safari is stored?