You should be able to do this in .htaccess. See:
https://httpd.apache.org/docs/2.4/rewrite/remapping.html#movehomedirs
The simplest is RedirectMatch:
RedirectMatch "^/wiki_old_dir/(.*)" "http://example.com/wiki_new_dirl/$1"
Any links directed to the old will be redirected to the new, assuming that you have retained the same directory structure and pages.