your output format is json. So you can parse your json to get count.
var start = "{ id: 'UC-lHJZR3Gqxm24_Vd_AJ5Yw', count: 76239202, name: 'PewDiePie' }";
dynamic result = JsonConvert.DeserializeObject(start);
var count = result.count;
Console.WriteLine(count);
7
solved C# How to get only one string from a website [duplicate]