Problem in clearing / deleting the previous content of array

Sir, how can I clear the previous content of an array?

void save()
{
  inbox_no++;

  
    if (inbox_no == 0)
      {
        
        inbox[inbox_no] = strdup(parSMS);
          
      }

 else if (inbox_no >= 1)
     {
    ---- cear the content of inbox[0] ------
     inbox[0] = strdup(parSMS);
     inbox_no = -1;
     }

}
    ---- cear the content of inbox[0] ------
     inbox[0] = strdup(parSMS);
     inbox_no = -1;

Do you KNOW what strdup() does? It allocates memory. When you are done with that memory, you need to free it.

    if(inbox[0])
      free(inbox[0]);
    inbox[0] = NULL;