Display the temperature using the LCD
From the information you provided, the answer is very simple.  If the sensor has an output of 10 mv/C, then the indicated temperature is found by dividing the sensor output (in millivolts) by 10.  For example, if the sensor output is 100 mv, then the temperature is 10C. You may need to scale your ADC output to obtain the sensor output in millivolts depending on the ADC reference voltage and resolution.