var list = new List<string>();
var regexPattern = new Regex(@"b(?:https?://|www.)S+b", RegexOptions.Compiled | RegexOptions.IgnoreCase);
var text= "https://www.instagram.com/r10net asdasc 1 ka sa ffg https://www.instagram.com/r11net dcgsfdg sdgfdsfs sdfsdfds 222222 4345";
foreach(Match m in regexPattern.Matches(text))
list.Add(m.Value);