iXelper

static void Main(string[] args)
        {
            string[] arrDate = { "09.08.2018  13:04:07"
                                , "11.05.2018  11:03:00"
                                , "16.07.2018  13:28:12" };

            string[] arrFileName = { "nameFile_1301_1602__2018_08_09__13_04_07_990"
                                    , "nameFile_1302_1602__2018_05_11__11_03_40_910"
                                    , "nameFile_1302_1602__2018_07_16__13_28_12_950" };

            foreach (var strDate in arrDate)
            {
                var pattern = GetSearchPattern(strDate);
                if (pattern!=null)
                {
                    var fileName = arrFileName.FirstOrDefault(f=>f.Contains(pattern));

                    if (fileName == null) continue;

                    string otvet = "Дата: " + strDate + "Файл с этой датой: " + fileName;

                    Console.WriteLine(otvet);
                }
            }
        }

        static string GetSearchPattern(string strDate)
        {
            DateTime date = new DateTime();

            if (!DateTime.TryParse(strDate, out date)) return null;

            return date.ToString("__yyyy_MM_dd__HH_mm_ss_");
        }

List<string> text = ["89192864554","+7926?874?22?44", "vk@yandex.ru" , "vk.com", "youtube"];
List<string> phones = new List<string>(text.Where(x => x.StartWith("+") || x.StartWith("8")));
List<string> sites = new List<string>(text.Where(x => x.Contains(".") && !x.Contains("@")));
List<string> email = new List<string>(text.Where(x => x.Contins("@")));