They are all equally precise, because the amount of yarn that you will need for a sweater varies by much more than the differences between those numbers.
31 dm has 2 sig fig 312 cm has 3 sig fig 3 m has 1 sig fig 3124 has 4 sig fig 3124 mm has the most significant figures (4), so is "more precise" than the rest. [Though for yarn, being that precise is a not a good idea as yarn stretches - that's why it's usually sold by weight for a given ply, with a given approx length.]
A Bill Cosby sweater is another term for a Cosby sweater, an oversized sweater featuring a loud, kitschy pattern.
there isn't a prefix for sweater
The sweater was made of wool. They attempted to make a sweater from the bags.
A sweater that buttons up in the front is called a cardigan.
A sweater may be any colour.
Hannah Montana sweater
It's an argyle sweater, not a sweater vest.
The possessive form is: the girl's sweater.
That's a nice sweater!
Sweater - EP - was created in 1998.
The Hockey Sweater was created in 1979.