How do I backup my saves on skyrim for a mod? [duplicate]

On WIndows 8, or at least on my system, the path is C:\Users\[username]\Documents\My Games\Skyrim\Saves. Naturally, it's possible you have configured your system differently: different drive, for example. If you are using Nexus Mod Organizer and virtual profiles, you have to go to the mod organizer's folder and find your profile in the profiles folder. Each profile will have a folder named after the profile and will contain a saves folder. Other virtual profile applications will likely have a similar arrangement.

I don't believe Windows 8 changes the location of the my games folder, so instructions for Windows 7 ought to work. In any case, the mod most likely does not mean to back up the literal save files, but rather to create a save of your game before the mod is installed. Any mod that uses scripts can permanently change your save file even after the mod is uninstalled (some even provide uninstall instructions to run specific scripts through the console or use the Mod Configuration menu from SkyUI), so if the mod does break your game you will likely have to load a save which was made before the mod was installed in order to get rid of its changes.