How to redirect WP post with a specific word in the URL

I’ve changed the URL structure of my WordPress post (not page) from:

mysite.com/archive/xxxxx

to:

mysite.com/post-name

The xxxxx is id number of post not post name, my problem is my post archive in google like example.com/archive/xxxxx and i am change my link like example.com/post-nam .

So when any user open my site from google its show him 401 error.

I’d like to redirect the old structure /post/ to the new one via .htaccess, or plugin

Thanks in advance.