stolen phone

You cannot transfer to a new phone, but you can get a refund on any unused portion and then use that to purchase AppleCare for the new phone. See this, Cancel or change the payment method for your AppleCare plan - Apple Support The only transfer you can do is for a new owner of your old device. AppleCare stays with the device, not with the person that purchased it. Transfer your AppleCare plan - Apple Support

Unless you had AppleCare+ Theft and Loss, you cannot according to the AppleCare terms and conditions.