Computer Configuration > Administrative Templates > Firefox > Browser Data Backup
Both
HKLM\Software\Policies\Mozilla\Firefox\BrowserDataBackup
If this policy is enabled, browser profile data can be restored from backups when restore is supported on the platform. If this policy is disabled, browser profile data cannot be restored from backups. If this policy is not configured, restore availability follows the platform default. This policy cannot be used to enable restore on platforms or in configurations where restore is not otherwise supported.