Nostalrius Begins - Quality wow vanilla realm (1.12)

Currently trying to extract some addons into my game client through the typical 'interface' - > 'AddOn' folder however the AddOn folder does not exist and the interface folder is completely empty. I've tried to create the addon folder but when I attempt to extract my addons into this folder I get the below message.

Extracting to "C:\Program Files\World of Warcraft\Interface\AddOns\"
Use Path: yes Overlay Files: no
Error: Unable to create "C:\Program Files\World of Warcraft\Interface\AddOns\OneBag\BagSlot.blp"
Irrecoverable Error: File creation error.

I've never had addon problems before so this is the first. I have no clue what to do but any help would be appreciated.

You can't extract directly into the program files, extract to your desktop or some place else then move them to the program files, you will then receive a prompt asking for permission to move the files.

It's been awhile since I have done this but I've seemed to forgotten this very important step. I will try this tomorrow. Thank you for your response!