Arduino Uno ds18b20 and sure 2416 dor matrix display

Using Arduino Programming Questions
24 
  // returns temperature in degrees C
  float getTempC(uint8_t*);

  // returns temperature in degrees F
  float getTempF(uint8_t*);

  // Get temperature for device index (slow)
  float getTempCByIndex(uint8_t);
  
  // Get temperature for device index (slow)
  float getTempFByIndex(uint8_t);

So, yes all the methods to get the temperature return a float, not an int.

Your buffer will need to be larger, and you'll need to use ftoa(), instead of itoa(). After that, you'll need to put more characters to the display.