The default location of DHCP backup is %systemroot%\System32\dhcp\backup and is backed up automatically every 60 minutes.
If you want to change the backup interval open the Registry Editor (
If you want to manually backup DHCP database then open DHCP console, right-click the server and select Backup
Select the location you want to save the backed up files and click OK
If you want to Restore DHCP database then right-click the server and click Restore
Select the location with the backed up files and click OK