If your goal is really to print the value from XML, you don't need to worry about types, as long as you believe the XML to be correctly formed. The value given withing the XML file is in all cases, a character string (representing - just print it. The conversion from string to variable (sprintf()) and back to string (Serial.print() or printf()) is unnecessary

If your goal is really to print the value from XML, you don't need to worry about types, as long as you believe the XML to be correctly formed. The value in the XML file is already character string just print it. The converting from string to variable (sprintf()) and back to string (Serial.print() or printf()) is unnecessary.