That's not possible.
You can not convert a value which is in "hh tt".
The result of such format will be something like "11 AM", "02PM", etc.
If you just want to get "11" or "2" then you can do something like -
i = Convert.ToInt32(lbltime.Text.ToSubstring(0,2));
lbltime.Text = i.ToString();
But looking at your code, you already are showing a value in format "hh tt", then why do you need to overwrite it immediately in the next line.
If you want to show the time in "hh tt" format, just remove the last 2 lines. Following should be enough.
lbltime.Text = DateTime.Now.ToString("hh tt");
And if you want show just the hours, then something like following should help-
lbltime.Text = DateTime.Now.ToString("hh");
Please let me know if your requirement is something else.