Thats not how mhwd works …
Or pacman.
If you wanted to see your installed packages then you could use
pacman -Qs nvidia
And if you wanted to remove a package, along with save files and unneeded dependencies, then
sudo pacman -Rns PACKAGE
…but …
We handle drivers using mhwd, so you probably dont want to mess with the packages themselves unless you know what you are doing or already broke something …
In mhwd we use the bus identifier … ex:
sudo mhwd -i pci video-nvidia
To see mhwd info you can use something like
mhwd -l -d
Which will show both installed and available profiles.
PS - for a review of mhwd-kernel see this recent thread:
Update kernel and was wondering if this is good news or not - #8 by cscs