getting the uploaded mht file link back to application

This logic is pretty depending on the developer side as the developer decides where to store the file.

For eg: After uploading the file, the folder to be saved is Files.  In this case the absolute path in server side is "~\Files\abc.mht".

After the operation, you can give back the above url to the user through a HyperLink control;

Eg:  HyperLink1.NavigateUrl = "~/Files/abc.mht";