This will replace all the existing GPO settings on a single GPO when you import. This is good when you have multiple domains and you don’t want to create your GPO settings from scratch so you would use the backup and import feature in GPMC.msc
Open group policy management > expand you domain > select your group policy objects > Right click on the gpo you want to backup > select Back Up…
Select a location and description > click Back Up
Once completed > click Ok
This is how it looks in the location
Now we will do the import to override all the setting on that single GPO, with the one from the backup.
Right Click the gpo > select import settings
Click next
Select the Folder location it is located > click next
Click next (This is a empty GPO no need to backup)
It picks up the GPO from the backup > Click next
Click Next
Click Finish
Click ok
All done new settings will be applied to your single GPO