I haven't seen a vB5 > phpbb3.2 convertor yet. Perhaps a vB4 > phpBB3.2 might work, but no guarantees are given.
I have no experiencence with converters but you should read through the topics here. In fact if I recall correctly there is no converter to phpBB3.2 yet and you should first convert to 3.0 (but this is going from memory - not always 100% trustworthy).
That is exactly why I wrote that I don't know of any vB5 converter.