Have a look at these links.... Looks like opera may not be a direct option. see screenshot https://support.mozilla.org/en-US/questions/1187286 https://support.mozilla.org/en-US/kb/import-data-another-browser https://support.mozilla.org/zh-TW/questions/931675

Unfortunately, all of these are about importing browsing history and bookmarks, as I understood them.

The screenshot also mentions passwords. Opera browser is not an option.

You could try exporting from Opera as a .csv (if Opera does that) and importing that into Firefox but you will run foul of the bug linked below. A fix is mentioned in comments on the bug and in a thread on Reddit. You have to change a preference in about:config to true to enable the import. signon.management.page.fileImport.enabled

https://bugzilla.mozilla.org/show_bug.cgi?id=1781213 https://support.mozilla.org/en-US/kb/about-config-editor-firefox

You could try exporting from Opera as a .csv (if Opera does that) and importing that into Firefox but you will run foul of the bug linked below. A fix is mentioned in comments on the bug and in a thread on Reddit. You have to change a preference in about:config to true to enable the import. signon.management.page.fileImport.enabled https://bugzilla.mozilla.org/show_bug.cgi?id=1781213 https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Thanks, worked great.