Now that you know the model, it might be possible to google up an online owners manual. I was able to find one for my filter that way.
The main reason to know the square feet is because that tells you how much DE to use. For example, in my filter, 36 ft wants 4.5 lb, and 60 ft wants 7.5 lb (i.e. 1.25 lb per 10 sq ft). I don't know whether those ratios apply to all DE filters.
--paulr
(Edited to fix a slipped decimal point.)