The best way to work with CDR graphics is to of course use the default software for this format - CorelDRAW graphics suite. However, not all users have access to this somewhat expensive software, and have to rely on some 3rd party editing conversion tools.
WMF (Windows Metafile) is also vector format, this will make the conversion easier. You can try some open source programs like Inkscape to open and export CDR graphics. This works best for older .cdr files, because 3rd party tools usually just support older version of CDR format and may not work with latest editions of CDR format flawlessly.