sudo apt-get install nautilus-open-terminal

other way.... ref

1. Close any open file browsers windows (just to be safe).
2. System > Administration > Synaptic Package Manager
3. Search for "nautilus-open-terminal"
4. If you do not see it you need to add the "Universe" repository: https://help.ubuntu.com/ubuntu/deskt...ositories.html
5. Mark it for installation then click Apply.
6. Open a new file browser and right click a folder. You should see "Open in Terminal". If you do not then log off and log in again.

ref

sudo add-apt-repository ppa:noobslab/apps
sudo apt-get update
sudo apt-get install open-as-administrator

and restart nautilus

killall nautilus && nautilus &