You want it to print mm instead of cm in the console?
If so change the abbreviations in the sketch:
Serial.println("cm");
to
Serial.println("mm");
And do as john21403 says to mathematically convert cm to mm.
You want it to print mm instead of cm in the console?
If so change the abbreviations in the sketch:
Serial.println("cm");
to
Serial.println("mm");
And do as john21403 says to mathematically convert cm to mm.