Thank's dude! I went to Mac'S menu bar>Go>Go to Folder>/System/Library/CoreServices/Go to /Library/PreferencePanes, then select the Software Update pane. Drag it to the dock and boom! You can try to find the ICNS for Software Update, create an alias first, then update the alias icon, then place on the Dock, if you want the icon to look nicer. I believe the ICNS file can be found in /System/Library/CoreServices/CoreServices.bundle (or something like that, I'm not at my Macintosh right now), right click, Show Package Contents, then search for it.
You can also long hold the System Preferences icon on the dock, then select Software Update from the list and open.