The command line is exacting. You must have spaces and hyphens
and underscores completely perfect and in order to run a command...
Most people copy and paste their commands because it's faster than
typing them and potentially getting them incorrect... In Synaptic
Package Manager: Click System>Admin>Synaptic, where all the additional
software for Ubuntu is located. It's a HUGE list. Be careful what
you install at first or it will take a long time to install, and you
could make a big mess! (as I once did!) As far as I know, dpkg is
automatically installed with the Ubuntu Install. You don't need to
type the command if the dpkg package is already installed. You will
only want to install dpkg-dev from Synaptic Pkg Mgr, if you want to
use Debian commands in the terminal for installing and compiling other
outside software, but I am finding it complex... I believe your
command for the dpkg-dev installation command is: dpkg --configure -a
:INCLUDE THE SPACES... This will then allow you to copy and paste, or
type other commands to install software not found in Synaptic or
Applications/Add/Remove. rots-a-ruck, have fun with learning it...