Look for the product sticker on the back of the TV. It is usually located in the lower right corner or in the lower center of the back of the TV. Hold the mirror behind the TV so that you can clearly see the label from the front or side of the TV. You can find the serial number of your Sony TV on the product label attached to the TV and in its original packaging.
The sticker also includes the model number of the TV, and you can differentiate it from the serial number because the model number contains letters. The product sticker must be on the back of the Sony TV, in one of the corners.