Major version upgrades are not straight forward yet on Frappe Cloud. But if you want to upgrade your site, say from Version 12 to Version 13, here's what you can do:

1. Go to the site dashboard by clicking on the site you want to upgrade.
2. Take a backup of your site by going to the Backup & Restore tab and clicking on Schedule Backup.
3. After the backup is complete, click on the 3-dot menu and download all the 3 backup files.
4. Now, if you want to keep the same URL, you can drop your site and create a new site with the same URL. Or if you want to test the upgrade, you can create a new site with a different URL.
5. From the New Site screen, enter the URL.
6. Select the version you to want to upgrade to.
7. Select the same apps that your old site had.
8. Upload the 3 backup files one by one on the Restore step.
9. Select a plan and click on Create Site.