Permalink structure messed up

I upgraded from 2x early February and everything has been fine (except I can’t delete or post pages to the blog or delete some comments in the moderation queue, but that’s another story). Today I logged into Google Webmaster toolbar and it showed tons of posts from 2006-2007 being 404s. According to Google the first signs of these 404s were around the time of the upgrade, so I assume that’s what caused it.

Google console shows about 75 404s going to this permalink structure: /blog/%year%/%month%/%day%/%postname%/

My permalink structure in settings in simply /blog/%postname%/ and to my knowledge always has been. The 404 posts all work with the current permalink structure in my WP settings. My question is how can I 301 all requests to that are going to the old structure to the new one?