f150 to 99 explorer radio/cd swap

You only need to use the plug on the right of the picture you posted.  I can tell you where the constant and switched wires are on the radio.  The plug nearest the edge of the radio is the one you need to be concerned about.  It has 2 rows of pins on it.  One row has the outer pins that are offset a bit.  The offset pin and the pin next to it (on the edge of the plug that is at the edge of the radio)  are switched and constant power.  If you ground the chassis of the radio and apply power to those 2 pins, the radio will come on.

Metra does make a harness that will plug into most factory radios. You should check and see if they make one for that deck.   metraonline.com