No, if there is no power, you cannot plug in a freezer. Freezers require electricity to function, and without a power source, they will not operate. In a situation where you are locked inside a walk-in freezer and there is no power, you would not be able to use the freezer's electrical systems, including the cooling mechanism or any lights or alarms that rely on electricity.
In such a scenario, it becomes even more important to focus on conserving your body heat, attracting attention, and waiting for rescue. Follow the previous steps mentioned to stay warm, make noise, and try to communicate your situation using any available means such as emergency buttons or intercom systems, if they are still functional despite the power outage.