// Use this in your power() function
int my_power;

// Needed by the test
int answer;

void setup() {

  Serial.begin(9600);

  // Should be 9
  answer = power(3, 2);
  Serial.println(answer);

  // Should be 5
  answer = power(5, 1);
  Serial.println(answer);

  // Should be 1
  answer = power(9, 0);
  Serial.println(answer);

  // Should be 16384
  answer = power(2, 14);
  Serial.println(answer);

  // Should be 0
  answer = power(0, 4);
  Serial.println(answer);
}

void loop() {
  // Do nothing
}

int power(int x, int y) {

  // Special case: if y is 0, return 1
  if ( y == 0 ) {
    return 1;
  }

  // Store x argument in the my_power variable
  my_power = x;

  // Count down using y. Multiply my_power by x for each iteration
  while ( y > 1 ) {
    my_power *= x;
    y--;
  }

  // Return the accumulated value in my_power
  return my_power;
}

Simulator: https://tinkercad.com/things/6a6fC8yK1Er