How to print out all the steps in Merge Sort?

Question

I'm a 2nd year college student and we have this subject Data Structures and Algorithm and a newbie. My professor gives me task to code the merge sort algorithm but she lately added that it needs to display the partition (the image that I posted) in my code. This is the sample image that I want to have in my code after the "1st Partition". Thank you in advance I wish you all safe and sound!

and this is my code

#include <iostream>
using namespace std;

//Merge two sub arrays L and M into collection'
    //(array, lower bound, mid bound, upper bound)
    //(array, 0, 3, 7)
void merge(int collection[], int p, int q, int r, int series) {

  // Create L <-- A[p..q] and M <-- A[q+1..r]
  //  n1 = 3 - 0 + 1
  //  n1 = 4
  int n1 = q - p + 1;
  //  n2 = 7 - 3
  //  n2 = 4
  int n2 = r - q;

  //  L[4],  M[4]
  int L[n1], M[n2];

//for (int i = 0; 0 < 4 ; i++)
  for (int i = 0; i < n1; i++)
//L[0,1,2,3] = collection[0,1,2,3] = [3,10,21,47]
    L[i] = collection[p + i];

//for (int j = 0; 0 < 4 ; j++)
  for (int j = 0; j < n2; j++)
//M[0,1,2,3] = collection[4,5,6,7] = [4,15,38,59]
    M[j] = collection[q + 1 + j];

  // Maintain current index of sub-arrays and main array
  int i, j, k;
  i = 0;
  j = 0;
  k = p;

  //If else statement to determine whether (ASCENDING) lowest to highest or (DESCENDING) highest to lowest
  if(series == 1){
      // Until we reach either end of either L or M, pick larger among
      // elements L and M and place them in the correct position at A[p..r]
      //    (0 < 4  && 0 < 4)
      while (i < n1 && j < n2) {
      //if ( 3   <=  4  )
        if (L[i] <= M[j]) {
        //collection[0] =  3
          collection[k] = L[i];
          i++;
        } else {
          collection[k] = M[j];
          j++;
        }
        k++;
      }
  }else{
      while (i < n1 && j < n2) {
        if (L[i] >= M[j]) {
          collection[k] = L[i];
          i++;
        } else {
          collection[k] = M[j];
          j++;
        }
        k++;
      }
  }


  // When we run out of elements in either L or M,
  // pick up the remaining elements and put in A[p..r]
  while (i < n1) {
    collection[k] = L[i];
    i++;
    k++;
  }

  while (j < n2) {
    collection[k] = M[j];
    j++;
    k++;
  }
}


//------------------------MERGING-----------------------------
// Divide the array into two subarrays, sort them and merge them
            //(array, lower bound, upper bound)
            //(array, 0, 7)
void mergeSort(int collection[], int lb, int ub, int sequence) {
//if (lower bound < upper bound)
//if (0 < 7)
  if (lb < ub) {
    // m is the point where the array is divided into two subarrays
    // m = 0 + (7 -0) / 2
    // m = 0 + 7 / 2
    // m = 3
    int mid = lb + (ub - lb) / 2;

    //Call mergeSort
    //mergeSort(collection, 0, 3)
    mergeSort(collection, lb, mid, sequence);
    //mergeSort(collection, 3 + 1, 7)
    mergeSort(collection, mid + 1, ub, sequence);

    // Merge the sorted subarrays
    //merge(collection, 0, 3, 7)
    merge(collection, lb, mid, ub, sequence);
  }
}

//----------------OUTPUT---------------------
// Print the array
void printArray(int collection[], int scale) {
  for (int i = 0; i < scale; i++)
    cout << collection[i] << " ";
    cout << endl;
}


//---------------MAIN PROGRAM----------------
// Driver program
int main() {
  int array_size;
  int order;

  cout << "Instructions. Enter array size with a minimum of 4 and maximum of 16" << endl;
  cout << "Enter array size: ";
  cin >> array_size;
  cout << endl;

  if (array_size <=3 || array_size >= 17){
    cout << "Your array size is maybe below or above the array size limits. Please try again" << endl;
    exit(0);
  }

  cout << "In what order do you want to sort your numbers? Press [1] ASCENDING, [2] DESCENDING" << endl;
  cout << "Enter: ";
  cin >> order;
  cout << endl;

int collection[array_size];
  cout << "Enter " << array_size << " numbers: ";

  for (int u = 0; u < array_size; u++){
    cin >> collection[u];
  }

  int scale = sizeof(collection) / sizeof(collection[0]);

  cout << endl;
  cout << "Before Sorting: \n";
  printArray(collection, scale);

  mergeSort(collection, 0, scale - 1, order);

  cout << "1st Partition:";
  //RIGHT HERE

  cout << endl;
  cout << "Sorted Array: \n";
  printArray(collection, scale);
  return 0;
}