var linkParser = new Regex(@"b(?:https?://|www.)S+b", RegexOptions.Compiled | RegexOptions.IgnoreCase);
var rawString = "https://www.instagram.com/r10net asdasc 1 ka sa ffg https://www.instagram.com/r11net dcgsfdg sdgfdsfs sdfsdfds 222222 43453";
foreach(Match m in linkParser.Matches(rawString))
MessageBox.Show(m.Value);