When you get the new replacement hub… there is a Hub Migration Tool that has been spotted. https://community.smartthings.com/t/replace-hub-hub-migration-tool/268656. I haven’t seen any post in regards to anyone actually using it. Give it a try and do provide details. Users would be fascinated to hear about your experience with the tool.
Note: the tool does not show until you have the new hub and connected to your account (unless you have multiple hubs). Do not remove or reset the old hub at any point before the migration.
Can I ask what is broken with your current v3 hub?