GIMP Plugin Registry

Okay, so I was trying out this tutorial called '"smart" sharpening' and one of the first steps is to go to Image -> Mode -> Decompose, and then select LAB or HSV, but I don't have an 'decompose' option. I looked through the plug-ins but there's nothing about compose/decompose. I have the newest version of gimp, I think. It just says GIMP 2. But anyway, I have no idea about this kind of thing. Can anyone help? It would be much appreciated! Thank you ahead of time!