@leocg I got it, thank you.
Is there a way to automatically restore all bookmarks?

I also found an old bookmark file and tried to import it as a HTML file, but nothing happened

After reinstalling opera, I logged into my account and tried to sync my bookmarks. But out of more than 3,000 bookmarks, only one folder has been added.
Despite the fact that synchronization was turned on until I deleted the previous version of the browser.
I tried to restore manually, through the recovery of deleted files from the computer itself, but it did not work.

As a result, I went to the site sync.opera.com and there are all the synchronized bookmarks.
Is it possible to unload them and add them to the browser again?

Windows 8
Opera 95.0.4635.25