Hi Sorina,

Archiving is more about classifying information/content that is either outdated or not being accessed that frequently by the visitors into a separate section on your site. I would not no index those pages because they might be ranking well in the search engines and still be getting traffic to the site. You can do this creating an "archives" section on your site so that if the visitors want to access the old content on your site they can still do so by accessing that section.

Here is a useful post on archiving content on your site