I found this today. https://www.airport.kr/ap/en/dep/depCargoSchList.do you can just look at cargo leaving and select just UPSIn combing through this thread, it looks like most phones went from ZhengZhou, CN to Incheon, Korea then to Anchorage.
Lately, some have been going through Tokyo (NRT).
I can’t find any solid route information for phones that ship out of Shanghai.