No instance of overloaded function matches argument list

#define _CRT_SECURE_NO_WARNINGS
 #include <iostream>
 #include <string>
 
 using namespace std;
 
 class String
 {
 private:
 char str[100]; 
 char cpy[100];
 public:
 
 static const char NULLCHAR = '\0';
 
 String()
 {
  str[0] = NULLCHAR;
  cpy[0] = NULLCHAR;
 }
 
 String(char* orig, char* cpy)
 {
  Copy(orig, cpy);
 }
 
 void Display()
 {
  cout << str << endl;
 }
 
 void Copy(char* orig, char* dest)
 {
 
  while (*orig != '\0') {
  *dest++ = *orig++;
  }
  *dest = '\0';
 
 
 
 }
 
 void Copy(String& orig, String& dest) 
 {
  Copy(orig.str, dest.cpy);
 }
 
 void Concat(char* orig, char* cpy)
 {
  while (*orig)
  orig++;
 
  while (*cpy)
  {
  *orig = *cpy;
  cpy++;
  orig++;
  }
  *orig = '\0';
 
 }
 
 void Concat(String& orig, String& cpy)
 {
  Concat(orig.str, cpy.cpy);
 }
 
 int Length(char* orig)
 {
  int c = 0;
  while (*orig != '\0')
  {
  c++;
  *orig++;
  }
  printf("Length of string is=%d\n", c);
  return(c);
 
 }
 };
 
 int main()
 {
 String s;
 
 s.Copy("Hello");
 s.Display();
 s.Concat(" there");
 s.Display();
 
 String s1 = "Howdy";
 String s2 = " there";
 String s3;
 String s4("This String built by constructor");
 s3.Copy(s1);
 s3.Display();
 s3.Concat(s2);
 s3.Display();
 s4.Display();
 
 
 system("pause");
 return 0;
 }