Store value in a variable with time format

Question

Hello every body, please could any one help me out there, i want to store value in a variable in a time format. for example if a user enter 3 on the console line the value should display like this  3:00:00. this is my code so far:

 

Console.Write("\n");

Console.Write(" {0,8}", "duration:\t");

length = Convert.ToString(Console.ReadLine(),@"d\.hh\:mm\:ss");

Console.Write("\n");

 

 but not working out. I appreciate any help from from any one. thanks