Not powered with extension cord.
First item is wire as described.
Second item is box presumably with outlet.
Third item is plug to show orientation to plug in as ascii pictured and
labeled.
Don't over think it.
Maybe this one is better:
~~~~~|_____| =----
Wire...box.. plug
I will not provide a boat load of background information for the
application as its not relevant to finding a solution, and usually winds
up as a huge distraction due to people picking at details instead of
helping with the solution.