Thanks to the wonderful help above, I found a good wire to use. In the rear panel, looking from left to right, I had this sequence of relays: empty-green-green-blue-empty in terms of relays. The 2nd from left green relay had the top middle pin activate 12v at key position 1. At key position 2, the leftmost (empty) relay plug had the top middle active 12v, the middle green relay had the right middle active 12v, and the rightmost green relay had the top middle active 12v. The blue and empty relay positions on the right side had no active 12v at any key position (well I mean they had a constant 12v feed but nothing that turned on with the key moving).

If anyone was interested, I used the leftmost position as it did not have a relay plugged in, and tapped the top middle wire. This feeds my 12v>5v USB converter well, and then the dash cam feeds of the USB plug. Ironically enough, not long after installing this, a drunk driver almost ran us off a cliff coming around a corner, and we got the footage, but the rear window just had so much dust on it that we couldn't make out the license plate number. Being a general failure at life, he did not have a front bumper (likely from a prior drunken incident) let alone a front license plate that would have been captured on our front camera.

Thank you everyone for all your help.