You may export and save contacts from Nokia .nfb backups and save them as separate vCard files (.vcf, .vcard etc.) which can then be used to transfer contacts to other software or devices. This can be done with various utilities for Nokia phones, such as Noki or NbuExplorer.
Convert Nokia PC Suite phone backup file to vCard contacts.
We found 2 software records in the database related to .nfb to .vcf file format conversion.
Microsoft Windows software - convert nfb to vcf on Windows
A small usefull program for exploring and extracting of files created with Nokia PC suite
Convert from nfb file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned nfb to vcf. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A free explorer for Nokia NBU files