By default, the backup account selected when you activated your Xiaomi smartphone is set, but if we subsequently added another Google Account, we'll be able to select or specify that account for created backups as well.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  About phone
Step 3:  Tap on  Back up and restore
Step 4:  Tap on  Backup account
Step 5:  Choose a  backup account
  1. Open the Settings
  2. Tap on About phone
  3. Tap on Back up and restore
  4. Tap on Backup account
  5. Choose a backup account

Xiaomi Instructions