I would use the String.Split(char[]) method and the String.SubString(int, int) method to inspect every 'country' inside your array and to get the number postfix of each country.

Try the following:

(The following code is now compiled and tested.)

Use a simple data structure to facilitate the task of holding the result of your operation.

public struct Result {

    string Country { get; set; }
    int Number { get; set; }
    int Occurrences { get; set; }
}


// define what countries you are dealing with
string[] countries = new string[] { "Pakistan", "India", "USA", "Iran", "UK", }

Method to provide the overall result:

public static Result[] IterateOverAllCountries () {

    // range of numbers forming the postfix of your country strings
    int numbersToLookFor = 4;        

    // provide an array that stores all the local results
    // numbersToLookFor + 1 to respect that numbers are starting with 0
    Result[] result = new Result[countries.Length * (numbersToLookFor + 1)];

    string currentCountry;

    int c = 0;

    // iterate over all countries
    for (int i = 0; i < countries.Length; i++) {

        currentCountry = countries[i];

        int j = 0;

        // do that for every number beginning with 0
        // (according to your question)

        int localResult;          

        while (j <= numbersToLookFor) {

            localResult = FindCountryPosition(currentCountry, j);

            // add another result to the array of all results
            result[c] = new Result() { Country = currentCountry, Number = j, Occurrences = localResult };

            j++;
            c++;
        }
    }

    return result;
}

Method to provide a local result:

// iterate over the whole array and search the
    // occurrences of one particular country with one postfix number
    public static int FindCountryPosition (string country, int number) { 

        int result = 0;
        string[] subArray;

        for (int i = 0; i < arr1.Length; i++) {

            subArray = arr1[i].Split(',');

            string current;

            for (int j = 0; j < subArray.Length; j++) {

                current = subArray[j];
                if (
                    current.Equals(country + ":" + number) &&
                    current.Substring(current.Length - 1, 1).Equals(number + "")
                 ) 
                    result++;
            }
        }

        return result;
    }

The following should enable you to run the algorithm

    // define what countries you are dealing with
    static string[] countries = new string[] { "Pakistan", "India", "USA", "Iran", "UK", };

    static string[] arr1 = new string[] { 
        "Pakistan:4,India:3,USA:2,Iran:1,UK:0",
        "Pakistan:4,India:3,USA:2,Iran:1,UK:0", 
        "India:4,USA:3,Iran:2,UK:1,Pakistan:0" 
    };

    static void Main (string[] args) {


        Result[] r = IterateOverAllCountries();
    }

The data structure you are using is not rich enough to provide you with that information. Hence you need to parse your string and create a new data structure to be able to provide (sring[][]):

        string[] arr1 = new string[] { 
        "Pakistan,India,USA,Iran,UK",
        "Pakistan,India,USA,Iran,UK", 
        "India,USA,Iran,UK,Pakistan" 
            };

        string[][] richerArray = arr1.Select(x=> x.Split('\'')).ToArray();
        var countPakistanIsFirst = richerArray.Select(x=>x[0] == "Pakistan").Count();

UPDATE

You seem to have changed your question. The answer applies to the original question.