number of pages in case of an article

why does endnote do not mention the pages number when it refers to an article ? though in the reference there are pages number

You mean how long it is (like a book does sometimes when you quote a book chapter)?  – I have never seen that in bibliography reference, just the span of pages.  

 along my article not in the bibliography, I can not add the pages to the footnote since it ends with a dot and does not exept the pages number

why and what can I do to fix this ? 

Pleae attach your output style (.ens) or if it is installed or downloaded and unaltered, the name.  But I usually just type it the way I want it to appear in the footnote (depending on the style).