I'm not sure I understand what you're trying to do. What browser are you using right now? Opera 22? Opera 12.17? Another browser. Where do you want to reinstall your bookmarks too. What browser? Now this re-installation of Windows should be no problem. You just save your browser profile to a Flash drive or to the cloud if you have that capacity, and then after you reinstall Windows, you reinstall the same browser, and then copy the profile into the profile of the browser, per the discussion below.
https://forums.opera.com/topic/3455/no-straight-forward-way-to-export-bookmarks-_____/2

Thanks for responding.
It's weird that opera doesn't have a way to export bookmakrs and i need to do this tricky part..
is there a way i can save them as HTML file and input them in Firefox?

i want to export my bookmarks into another browser and I don't know how.
i need to reinstall my windows and i have planty of websites bookmakred, so i don't want to save each one individually

any suggestions?