So... You're asking what the average length of a sword used by the Assyrians is?
From what I gather in the image you show, assuming they are Assyrians from whatever timeline you're looking into specifically...
The blade appears to be shaped similar to the kind used by 'vikings.'
The grip seems to be an assortment of ball and rounded shaped parts on the tang, with a very Scandinavian pommel. Another odd thing is the way they sheath their weapons, through the folds of their robes.
As for dimensions, I don't think the ancients often cared too much for proportions in their art, but the swords shown there could be depicted properly for all I know of such weapons. They sure seem to be properly sized compared to the persons wearing them.
Based purely on that image, I would say your guess is right.