Reseting Apple Watch after death of ower

My father recently passed away and we are trying to reset his Apple Watch. His Iphone has already been turned into US Celluar and his Ipad isn't accepting his Apple Password. We have also already closed his email account. How can I reset his Apple Watch and clear the Activation Lock now?

I've tried the suggestion from the communities board dated May 26, 2021 by trying with my computer, but because his Apple password isn't working on his Ipad it is asking for verification and that is sent to his Iphone via Text or his email address which we don't have access to any longer.