Hi,
best to start with is the site migration guide from Joomla!.org at
docs.joomla.org/Migrating_from_1.0.x_to_1.5_Stable
This guide includes the database migration.
Another way would be to export the old fb tables from your sql database and then import them into the new sql database. There you have to watch out for several issues:
1. Make sure that you do not have conflicts with the sql versions
2. The tables of the old database of joomla 1.0... have usually a different database prefix than the new joomla 1.5...(jos_).
As I am not an expert on sql databases, I recommend going with the migration guide, back-up old sql database and new, migrated database.