[Makarov]

function splitToParts(fullKm){
    var kilometers, meters, santimeters, millimeters, rest;
    kilometers = Math.floor(+fullKm); 
    rest = +fullKm - kilometers;
    rest *= 1000;
    meters = Math.floor(rest);
    rest -= meters;
    
    rest *= 100;
    santimeters = Math.floor(rest);
    rest -= santimeters;
    
    rest *= 10;
    millimeters = +rest.toFixed(2); 
    alert('Километров: ' + kilometers +
          ' Метров: ' + meters +
          ' Сантиметров: ' + santimeters + 
          ' Миллиметров: ' + millimeters);
}
splitToParts(3.1415926);