Is this the correct way to do it, since I'm new to C#
Console.WriteLine("please enter m,y,n: \n");
double month, year, numberOfMonths = Convert.ToDouble(Console.ReadLine());
You can do it by asking user to enter the values split-ed by some delimiter like space, semi colon etc. And then split the value and parse accordingly. for example
string input = Console.ReadLine();
string[] split = input.Split(',');
double month = Double.Parse(split[0]);
double year = Double.Parse(split[1]);
double numberofmonth = Double.Parse(split[2]);
Ofcourse the above code is not the most elegant/efficient/error free code. But, it is just written to get the idea across.