Hello Michiteru Sugitani
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
Q1: To locate your existing VMs, you can go to the Azure portal and navigate to the Virtual Machines section. From there, you can see a list of all your existing VMs and their associated images.
Q2: Yes, that's correct. The old publishing account images will be deprecated in April 2024, which means that VMs created with those images will no longer be supported. It is recommended that you migrate your VMs to the new Rocky Linux image before the deprecation date to ensure continued support. The migration process is outlined in the document you provided.
Hope that helps.