Sorting directory files and getting the highest file name

I have a directory with 40 files with names from 0 to 39 (for example), I am trying to get the file with the largest number in its name (which means I need to get "39") I am trying to sort the directory.. I have tried using the following topics:

How to retrieve list of files in directory, sorted by name

Sorting the result of Directory.GetFiles in C#

Nothing works for me.. I tried each of the methods - using Linq and the others.. and I dunno why..

I get the following result of the sorting (check picture below):

Thanks for the help,

Din Bracha.