Where can I find the Zhengzhou Epidemic Pass Code?

It can be viewed in the WeChat State Council client.

Starting from March 13, 2020, the China Academy of Information and Communications Technology has joined forces with China Mobile, China Unicom and China Telecom, the three major basic telecommunications operators, to obtain mobile phone "signaling data" through the base station location of the user's mobile phone. ”, a free query service provided to 1.6 billion mobile phone users across the country. Mobile phone users can use this service to query information about all cities and towns they have visited in the past 14 days.