However, there is no ‘tab’ called Existing Backups. At the bottom of the page there I can see the backups that have been made. But there is no download button. Only restore or delete or other.
In the backup/restore tab, click on the element you want to restore, for example in the screenshot below if I want to download the plugins portion backup I would click on the “Plugins” button: https://snipboard.io/mx7taO.jpg
A number of files should then appear above: https://snipboard.io/JhntOM.jpg and you can click the “Download to your computer” button.
For your DB you will only ever have one file. For your files you may have multiple files. The number will depend on the size of your site and size of your archive split.
You should be able to select multiple files in Google Drive. Google drive will then bundle them together to create a larger zip files (if you have a a large number of files, it may be in two or three zip files)