You can use the Nokia PC Suite program to export the contacts from an .nbf file to a CSV format and then use any of the available csv to vcf converters to generate your vCard contacts file. However, the more typical extension used is vcf suffix, so if you need vcard you will have to rename vcf to vcard.
Convert Nokia phone side backup file to vCard contacts file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert nbf to vcard on Windows
A free explorer for Nokia NBU files
Convert from nbf file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.