By default in Gnome 3, Nautilus URL bar is not available within the window.
If you want to type an URL such as a path towards a smb share, Just type Ctrl-L key combination.
If you want to make this URL bar available for each session, there are two ways to do it : dconf-editor or the command-line tool gsettings
Within the dconf-editor GUI program, go to : org>gnome>nautilus>preferences and set ‘Always use location entry‘ to true.
With gsettings, get the current value for gsettings get org.gnome.nautilus.preferences always-use-location-entry
Set this parameter to true : gsettings set org.gnome.nautilus.preferences always-use-location-entry true