how to divide the row in multiple when 3 comma will come

This Method would split the given String every newLineEvery fields (separated columns by comma)

public string FixAddress(string address, int newLineEvery = 3){
	if(String.IsNullOrEmpty(address))
		return address;
	string separator = ",";
	string newAddress = String.Empty;
	if(address.Contains(separator)){
		int elemCount = 0;
		foreach(string elem in address.Split(separator)){
			elemCount++;
			newAddress += (elemCount % newLineEvery == 0) ? "\n"+elem : elem; 
		}
		return newAddress;
	}
	return address;
}

Also behavior would be different if you are actually using MvcHtmlString instead of a string field here. (Html Linebreaks are different and also you would need to utilize MvcHtmlString.Create(newAddress) as Return of the function.

You may take the following approach-
1. Find the index of 3rd comma from the supplied string variable

public int GetNthIndex(string s, char t, int n)
{
    int count = 0;
    for (int i = 0; i < s.Length; i++)
    {
        if (s[i] == t)
        {
            count++;
            if (count == n)
            {
                return i;
            }
        }
    }
    return -1;
}

Reference: Find Nth occurrence of a character in a string

2.Remove the comma & add carriage return character after that index like

string yourString="sar john,texas,dellas,ny,111111,";
string finalString;
finalString=yourString;
int indexOfThirdIndex=0;
int counter=3;
while(indexOfThirdIndex!=(-1))
{
   int indexOfThirdIndex=GetNthIndex(finalString,',',counter);
   if(indexOfThirdIndex!=(-1))
   {
      finalString=finalString.Substring(0, indexOfThirdIndex).TrimEnd(',')+"\r\n"+inalString.Substring(indexOfThirdIndex);
   }
   counter+=3;
}

Hope, it helps :)
N:B: I haven't tested all these in my system but the approach should work. Please let me know if it doesn't.