You're going to struggle to do this, because the values in the Item column are treated as text. So the sorting looks at characters one at a time from the left until they're different, so 1 comes before 6 even if there are zeroes after the 1.
You could try to extract the numerical value into a different column but it won't be easy.
You could also try to edit the values so that there are leading zeroes, so instead of:
RING BINDER, plastic, 6mm x 1.2m
you have
RING BINDER, plastic, 06mm x 1.2m


and instead of:
STAPLE WIRE, heavy duty, binder type, 23/6
you edit it to:
STAPLE WIRE, heavy duty, binder type, 23/06


It'll get difficult when you have the likes of:
1 1/2"
and

1 3/8"
because the 3/8ths is smaller than the 1/2 numerically, but not alphabetically.