How to Back up in google drive

This support document outlines the natively supported backup methods - these being to iCloud or iTunes/Finder:

How to back up your iPhone, iPad, and iPod touch - Apple Support

If you wish to use Google Drive, you’ll need to use a third-party File Manager App that has the capability to Backup files to Google Drive. Due to the iOS/iPadOS Sandbox Security Architecture, third-party backup will be limited in that it can only ever be a partial backup - and will not necessarily include all files or iPad settings.

See this support article from Google:--> https://support.google.com/drive/answer/7070690?hl=en&co=GENIE.Platform%3DiOS

Since the above is not an Apple procedure, for any eventual inconvenience/issue/doubt contact Google support directly.

Regards

Giulio