GameObject[] in C#

see it:

GameObject[] ballArray
GameObject balls;
void Start()
{
    for(int i=0;i<5;i++)
    {
        ballArray*=Instantiate(balls,transform.position,Quaternion.identity);*
 *}*
*}*
*```*
*<p>why it can't work ?</p>*

You didn't initialize your array.

void Start() {
  ballArray = new GameObject[ desired size ];
}

Use the '101-010' button to format your code so people can read it, btw.