Haven't ever needed to do this, but one or more might be worth a try.
https://www.harmari.com/2014/06/access-deleted-expired-archived-craigslist-ads/
https://itstillworks.com/look-up-past-ads-craigslist-37107.html
https://www.reddit.com/r/craigslist/comments/2vrf88/help_me_reddit_i_need_to_view_a_deleted/
https://www.techwalla.com/articles/how-to-see-craigslist-ads-that-have-been-removed-cached