@Ron Every hosted Micro.blog site -- like yours and mine -- has it by default. Just add /archive to the URL of the site.

If it doesn't work then it is likely the person either removed the page or changed the URL for it; fortunately, the convention is to keep the link of your archive visible, as it is on our sites. For example, yours is at the top of your site, above your posts, whilst mine is at the bottom of my site, below my posts.