What normal mechanical keyboard provided is like above; the function key to adjust the multimedia volume.
Just pressing the combination keys of FN + F1 to mute the volume, FN + F2 to lower the volume and FN + F3 to increase the volume.
Mainstream mechanical keyboard all do provide this feature. i.e ducky

If you are looking for better volume controller, you may buy it separately from keyboard.
Dedicated volume controller, something like this Griffin.

More recommended if buy separately.

As Human10 recommend, you may choose something like this Greed Wolf.