The phrase itself is an example of an Operation Blank trope where a plan is given a code name so that it can be succinctly stated and acted upon. In this case, it's fairly descriptive. A Fire Sale is "the sale of goods at extremely discounted prices" and is often accompanied with the catchphrase of "everything must go!" with the implication that they are trying to get rid of the items even if at a loss.
Shortly thereafter, Skipper references that "everything must go", which hints at that their plan is to jettison as much weight as they can from the ship. The use of "West Helsinki" is, in my opinion, nonsense to make it sound more exotic, although Helsinki did experience a fire in November 1808, shortly after the Siege of Sveaborg that destroyed a quarter of the city, which could be the kind of obscure reference that a child's cartoon animator loves to put in to see if anybody catches it.