oxygen sensor harness

O2 Pigtail Was Cut Off, Bought A New One, Was Universal All Black Wires Dont Know Which Wires Connect To Which. Pigtail Was All Black But The O2 Sensor Wires Were 2 White 1 Grey And 1 Black. The pigtail That Came From The Car were White W A Black Stripe, Red W A Yellow stripe, Red W A Green...

Hey everyone, going to be replacing my o2 sensor harness in the next couple days with an extended one so I can have oxygen sensors, I was looking under the hood/under the car and was wondering Where is the main connector so I can swap them out? I can’t seem to find it... Thanks!