Page count? I dunno. Maybe a couple dozen pages. 90% of the content on my site is dynamic, so one page linked to my database could serve up tens of thousands of articles, for instance.
Or a page in my product catalog could serve up an endless number of items.
The login page is, of course, static in its content.
But I guess what you are getting at was how much rework I’d have, and I guess the answer is most of my pages are pretty intricate - at least to me - so re-designing them to be responsive would be a major task.
(You see me on here and how long it takes me to get one page working, well imagine retooling 40-50 pages?!)