C # insert data null

You could support me I'm new, I'm migrating data from Oracle to SQL server but the problem is that I'm trying to insert data and everything was fine, until I came up with the following: When inserting the data there are null fields and I do not know how to correct it.

  

** Error managerid there I have the null fields. managerid = reader3.GetInt32 (2);

It tells me there is no data and it causes error. **

//INSERT DEPARTMENTS
            cmd2.CommandText = "SELECT * FROM DEPARTMENTS";
            cmd2.Connection = conectar;
            cmd2.CommandType = CommandType.Text;

            SqlCommand insert3 = conectarsql.CreateCommand();
            insert.CommandType = CommandType.Text;

            int departmentid;
            string departmentname;
            int managerid;
            int locationid;
            OracleDataReader reader3 = cmd2.ExecuteReader();
            reader = cmd2.ExecuteReader();

            while (reader3.Read())
            {
                departmentid = reader3.GetInt32(0);
                departmentname = reader3.GetString(1);
                managerid = reader3.GetInt32(2);
                locationid = reader3.GetInt32(3);

                insert.CommandText = "INSERT INTO DEPARTMENTS VALUES('" + departmentid + "','" + departmentname + "','" + managerid + "'," + locationid + ")";
                insert.ExecuteNonQuery();
                //FIN INSERT DEPARTMENTS