Unfortunately, Google Nest requires the QR code or the 6-character setup code printed on the back of the Google Nest Hello Doorbell or the Google Nest Doorbell (Battery) in order to set up the doorbell. In addition, the previous resident or owner needs to have removed the doorbell from their Google Home app or Google Nest app (depending on the doorbell).
See this Google Nest Help "Moving guide for Nest devices" page:
See also this info "If you're moving and leave a Nest product behind":
I apologize for my late response and thank you for all of your patience while waiting for a reply. I'm terribly sorry to hear that you're having these troubles. I understand how upsetting this could be, but I'm happy to assist you with this obstacle. I am afraid that without the QR code, you are not able to install the device. Did you already throw away the packaging by chance? It should also be there.