How can I pick an especific random string up from an arrayString?

I have a situation where I received an input string with a random value contained there ("54403dd5-5f1d-4ba0-8477-9b16807ee285") basically that string is received from another source code but I just pasted there for reference, also notice that I split patterns in order to get a cleaner string output(this can be omitted). What I really need is how I can pick only that Id value up from there so I can process further. I also pasted the output generated with what I've done so far but not luck, If you have a better approach to get only this value without anything else I will appreciate.

String input = "\"{\"Protocol\":\"12345\",\"Version\":1,\"Timestamp\":\"2020-05-01T21:55:12.123456Z\",\"Assignment\":{\"Id\":\"54403dd5-5f1d-4ba0-8477-9b16807ee285\",\"Asset\":[]}}\"";
String pattern = @"\s-\s?[+*]?\s?-\s";
int found = 0;

String[] elements = System.Text.RegularExpressions.Regex.Split(input, pattern);
foreach (var element in elements)
    Console.WriteLine(element);

Console.WriteLine("\nWe want to retrieve only the Id string value. That is:");
foreach (string s in elements)
{
    found = s.IndexOf("Id");
    Console.WriteLine(s.Substring(found + 5));
}

Output:

"{"Protocol":"12345","Version":1,"Timestamp":"2020-05-01T21:55:12.123456Z","Assignment":{"Id":"54403dd5-5f1d-4ba0-8477-9b16807ee285","Asset":[]}}"

We want to retrieve only the Id string value. That is: 54403dd5-5f1d-4ba0-8477-9b16807ee285","Asset":[]}}"