How to remove old site URL format in Google

modify .htcaccess to tell google that /blog is your url. Something like this:

RewriteRule ^blog https://www.mysite.com [R=301,L]

Something along those lines I believe. Hope that points you in the right direction.

This might help too:

https://support.google.com/webmasters/answer/93633?hl=en

Hi Stoplosstm,

Thank you very much for your information.

I did that when migrating, but the problem is that I want to eliminate the old URLs from Google that still appears on searches… No offense to anybody, but I wonder if this is the forum to ask this question. Since it has to do with Google search results.

You can’t. The best you can do is redirect them to the new ones, and eventually Google will catch up.

You can see this, but note their important note at the bottom. It is not intended for simply removing 404s. Yup, Google will catch up.

You need to redirect, through 301 redirection all of your 404 errors will be resolved, You will observe drop in traffic but it will be back live after a month or so.

And for removing the pages and domain
https://support.google.com/webmasters/answer/164734?hl=en