Search String And Replace string in c++

#include <iostream>     
#include <string> 
#include<conio.h>      
using namespace std;
int main ()
{
string str ="Umer is a good programmer";

string str3;
string Replas;
int i=0;
char search_word[100];
cout << "enter Word For search :  ";
cin >> search_word;
while(search_word[i]!='\0')
{
i++;
}

size_t found = str.find(search_word);
  if (found!=string::npos)
  {
   cout << "-----------------------------------------------"<< endl;
    cout << "Location found for search Elements : " << found << '\n';
       cout << "-----------------------------------------------"<< endl;
    cout << "number of elements are :"<< i<< endl;
       cout << "-----------------------------------------------"<< endl<< endl;
      
    cout << "Enter Word for replace....";
    cin >> Replas;
     str.replace(found,i,Replas);
     cout << endl;
      cout << "-----------------------------------------------"<< endl;
     cout <<  str<< endl;
      cout << "-----------------------------------------------"<< endl;
     }
     else
     {
         cout << endl;
    cout << "-----------------------------------------------"<< endl;
     cout << "sorry word not found"<< endl;
      cout << "-----------------------------------------------"<< endl;
     }
getch();
}