int theInt = 123; //integer to be converted
char buffer[10]; //char buffer to hold converted integer up to 9 digits plus terminator
itoa(theInt, buffer, 10); //convert using base 10 and put result in string named buffer
tft.drawChar( 190, 100, buffer, ILI9341_WHITE, ILI9341_BLACK, 5);
Note that Strings were not used in this conversion