Ground wire connection question

Hi, I am a new member and I am trying to replace a light fixture in my house that I just purchased. I thought the wiring would be straightforward and I would be able to just take a picture of the assembly, remove the old and install the new the same way the old was installed. However, upon removing the old fixture, I noticed the ground wire had come loose and was not connected to anything. I have taken pics and actually drew out a diagram of how everything was pre-wired for you to see to help answer this question. I’m needing someone to tell me which lead or both I need to connect the ground to. The assembly has two leads, both with a white, black and copper wire inside. One lead is running in the direction of the switch so I’m assuming it’s running to the switch and the other lead is running to another fixture with its own pull switch on the other side of the wall and there is another lead coming out of that box that is running in the direction of the breaker box. The lead that is running to the other light switch’s white wire is connected the black wire of the lead that is running to the switch and the two remaining black and white wires were connected to the old fixture. The ground wire of the lead that was running to the switch was not exposed and the ground wire of the lead running to the other light fixture was pulled out and exposed so I would assume the old ground was attached to it but I don’t want to just connect the new fixtures ground to it without knowing for sure that that is where it needs to go. I would appreciate any help on this issue and thank you. I am going to attach a pic and the diagram for a better understanding of what is going here.