Assuming each date is on a separate line, you can read them all with
string[] lines = File.ReadAllLines(path);
You can then convert each one to a DateTime using Datetime.ParseExact, or DateTime.TryParseExact:
foreach (string line in lines)
{
DateTime dt = DateTime.ParseExact(line, "dd.MM/yyyy h:mm:ss tt", CultureInfo.InvariantCulture);
...
}
There is a list of DateTime format codes here:
Formatting a DateTime for display - format string description[
^]