Create Permalink In Blogger
When you are composing a new post entry, you may select either using automatic or custom URL in Blogger.
Sometimes you may need to create a custom by your own self rather that automatically created by Blogger.
So, you may have a look at the right side of your compose page. Go to Settings >> Permalink. Then select Custom URL and type the name of your URL.
When you publish your post entry, it will use the URL as per stated by you. You may have a try and good luck!