Edit your output style and add |, Pages|. to the end (with a link adjacent character between the comma and the “pages” field name) – you can copy this text from the journal template to the end of the Book Section template.
or or |, p.^pp. Pages|. if you want the p. or pp. to appear with the pages. – you can probably copy this from the Cell or other output style. It does seem odd that the Harvard styles don’t include this infomation.