Convert SPB to TXT

The only way how some kind of spb to txt conversion would work, is to convert spb to vcf using Samsung Kies, which is essentially export of contacts from Samsung phone backups and saving them in vCard format (.vcf). VCF is basically a specially formatted text file, so you can view it using any text editor. In any case, you will need proper version of Samsung Kies to handle .spb files.