You will need to export the bookmarks to an HTML file in Konqueror. Checking via Google there appears to be a couple of possible ways to do this.

In Konqueror in the bookmarks editor check the File menu, there should be an Export option that will allow you to export the bookmarks to an HTML file. If there is not an HTML option, there should be an option to export to Mozilla format instead. If you choose that option you may need to rename the file, I believe it will call it something like bookmarks.mozilla, you can rename that to bookmarks.html

You can then import that file into Firefox as shown in the importing bookmarks from an HTML file article.

You can go to Bookmarks > Edit Bookmarks in Konqueror.
"Export HTML Bookmarks" is at the bottom of the File > Export menu.

You can set the file name in both cases, "Export HTML Bookmarks" and "Export Mozilla Bookmarks", yourself.
Make sure that you add a .html file extension if Konqueror doesn't do that automatically.

That worked. Thank you !