When you installed HU, you used a file called Patch_D2.mpq. An mpq file is just like a .zip or other compressed file. The text files have all been compressed as a .mpq because that's the compression format Blizzard liked at the time they made Diablo2.
To decromess the mpq and read the text files, you just need to get software that handles mpq files, that can decompress them into their original files.
Here's a link to software that handles mpq:
http://www.zezula.net/en/mpq/download.htmlIf you've extracted the mpq normally (preserves folder hierarchy), then you should find the text files in this folder:
data\Global\Excel
It will help quite a bit to read the files in a spreadsheet program, since that will automatically align the columns along the tab characters. For the Matel de Fer, the columns "Level" and "Levelreq" are both 50 in the file weapons.txt.