Using the Nokia NbuExplorer, Noki or similar utilities for Nokia phones it should be quite possible to export the contacts from Nokia ARC backup files and save them in form of a vCard file (.vcf), which is what arc to vcf conversion most likely represents. Seems to be working just fine.
Open ARC file Open VCF fileA small usefull program for exploring and extracting of files created with Nokia PC suite
A free explorer for Nokia NBU files