The Google search engine maintains old copies of web pages in cache (storage space for resources). When you do a search, the results will show two links, one of which is labeled "Cache"; clicking on that brings up a stored copy of the page.
To recover an entire website, use the "site" feature of Google. In the search box, type "site:www.sitedomain.com" and follow it with a search term that's likely to bring up all the pages. For example, this search works:
Then, save out each page.