Electronics make my head hurt.

I have a used Tammy PIV and an older Spektrum Dx6 with a BR6000 receiver
The elevation has a servo installed
The previous owner unplugged the DMD from the receiver, so I am not sure what goes where

(I used a Futaba 4 channel for my other 2 tanks, so set up was easy plug and play)

The receiver has 7 open slots
Bat
Thr
Aile
Ele
Rud
Ger
Aux

The Tammy PIV Manual lists the channels as
Rudd Ch 1
Throt Ch2
M Gun Ch3
Turr Ch4

Since the order of the Spektrum receiver and the Tammy channels are in a different order, I am confused.
Where do I plug them in?
(Let's assume that they used the default set up with turret/elevation on left stick and throttle/steer on right.)

Also, this is a dumb question, but what color wire on the channel plugs are pos or neg?
The receiver does not have slots for the tabs on the channel plugs.

Originally there was a Pico Switch installed, which I have, but probably won't install.
I believe the Pico is like a kill switch?

Any help is appreciated.