Conduction - outer surface temperature

I have a rectangular shaped 120 x 120 mm object with a 8.8 mm thickness, i want to apply a temperature in the interieur surface ( blue one indicated in the image ) of that object equals to 120 degree celcuis, i want to know what would be the temperature at the outer surface of that object. if i simply do, then the temperature ll be all the same in all the object and the outer surface ll have a 120°c temperature also ( image 2 ), how can i solve my problem which consists of knowing the temperature at the external surface after applying temperature in the interior one.

SolidworksSimulation