Firefox-Lost that Download Arrow On Toolbar

[Jerry Dale]

I somehow deleted the green downward pointing arrow icon on the Firefox toolbar. I use it to open the folder of a downloaded file. I did not see a way to recover the icon in Firefox options.
Any clues?

Update: thanks for that solution (below). It worked.

 

[Alabalcho]

Right-click onto toolbar, "Customize". On the left pane, you will see items you can drag onto the toolbar, that "download arrow" should be there.