Google Search Console is still indexing old pages

I had changed the URL structure of my website 5 months back. Previously it was not country specific so I made it country specific by adding /[language-code]-[country-code]/ to the URLs.

Then I had updated my sitemap.xml file and uploaded it to Google Search Console, but I was still getting hits from the older URL. The problem was google search engine had indexed the older pages so every time someone searched for my website it will also show additional URL's as sitelinks which had old URL's.

To fix this I temporary blocked the URL's with the help of Google Search Console, there was a catch in that it only blocks a URL for a short duration and then the URL starts appearing again as sitelinks with my website's name in the search result.

How can I fix this? Is there a way to completely remove the URL from google search index?