plug 21 should plug into the harness in the dash since you don't have nav.
plug 2 goes to the factory antenna. Mine came with an extension cable for that to reach the back.
That should be all I think.
Since you don't have nav I wouldn't think a cable would be needed to reach the back like it is on the nav unit. What happens when you plug in 21 to the plug in the dash?
Does the radio power up?