To export your bookmarks, goto the URL opera://bookmarks, click the drop-down at the bottom left and choose "export bookmarks". That will save your bookmarks as an HTML file.
To export your passwords, goto the URL opera://settings/passwords, click the 3 dots to the right of "saved passwords" and chose to export your passwords. It will ask you for your Windows user account password to proceed. Then, it will save your passwords to a csv file. Open the file with a text editor to confirm that they're there.
Then, you'll want to put the 2 files on a USB stick or something to back them up.
Then, to import passwords, goto the URL opera://flags/#password-import and make sure the Password Import flag is enabled. If it's not, enable it and restart Opera. Then, goto the URL opera://settings/passwords, click the 3 dots to the right of "saved passwords", and point it to your csv file.
To import bookmarks, goto the URL opera://settings/importData, select "Bookmarks HTML file" in the drop-down, and point it to your HTML file.