How to get rid of thousands of topics that have no value?

There are over 25k topics on my forum and 90% of them have absolutely no value SEO wise (no backlinks or traffic) or content wise (they not relevant or useful anymore).

I could probably get a list of URL-s of all those topics by doing some bulk exports on Google Analytics and Google Search Console. However, i dont know if i should archive them, delist them or put in a special category. I dont want them to be indexed by Google, thats for sure.

Also, if i decide to archive them or move them somewhere, how do i do this in bulk?

You can have a look at Administrative Bulk Operations for some examples.