To revert your pages from blogs back to pages you'll need to go to the page history of each page and revert prior to the blog conversation. More information on this can be found at Create, edit, and publish a page | Page versions and history.
My above answer was not correct, I am further investigating how to revert a converted page to a blog.
There is a feature request related to this: Convert blogs to pages | CONFCLOUD-72088. I am working with the team to follow up on Convert any page to a blog in Confluence to ensure we communicate the risk of accidental page > blog conversion and a path to revert these accidental changes.
Hi @Dmitry Malysh @Stephen Sifers, thank you so much for pointing that out and passing on the feedback. Today, you aren't able to convert blogs back to pages. However, we completely understand this is a valid request and our team is actively working on adding it to our roadmap so we can bring this feature to customers as soon as possible! Thank you for your patience!