Firefox lets you import settings and information from Safari. This can be handy when you start using Firefox because it saves you from having to configure many things yourself.
When you run Firefox for the first time, the Import Wizard will ask if you want to import settings and information from other browsers you already have installed.
If you have already passed this step, you can still import your settings and information.
The Firefox Import Wizard does not yet detect Safari on Windows systems, but you can export your bookmarks from Safari, then import them to Firefox.
You have successfully exported your bookmarks from Safari, to import them to Firefox proceed to the next section.
Click the Bookmarks button and select Show All Bookmarks to open the Library window.
The bookmarks in the selected HTML file will be added to your Firefox bookmarks within the Bookmarks Menu directory.
Based on information from Import bookmarks (mozillaZine KB)