Need this is C++

I'm not sure what is missing in my code. Please fix

Write the implementation (.cpp file) of the Counter class of the previous exercise. The full specification of the class is: o A data member counter of type int An data member named counter!D of type int A static int data member named nCounters which is initialized to 0 o A constructor that takes an int argument and assigns its yalue to counter. It also adds one to the static variable nCounters and assigns the (new) value of nCounters to counterID A function called increment that accepts no parameters and returns no value, increment adds one to the instance variable counter o A function called decrement that accepts no parameters and returns no value. decrement subtracts one from the counter o A function called getValue that accepts no parameters. It returns the value of the o A function named getCounterID that accepts no parameters and returns an int. getCounterID returns the value of the data member counter. counterID SUBMIT 1 Counter::Counter(int counter) 3 this->ncounters 0; = 4 this->countercounter; 5 this->nCounters+ 6 this->nCounterscounterID; 7 8 void Counter:increment() 9 1 this->counter++; 12 void Counter::decrement() 13 14 this->counter--; 15 16 int Counter::getValue() 17 18 19 20 int Counter: :getCounterID() 21 return counter return counterID; 23