You won't find db user/name/host inside the mysql database.. it is stored only in includes/dbconnect.php.
BookingWizz creates all tables inside the database which you specify with bs_* prefix, so if you see bs_settings along with other bs_... tables -> that's the database which bookingwizz was installed into.
DB User / Host / Name can be found only in your hosting control panel. If you don't know where to look for that info - please contact hosting provider - they will know for sure. Also, you will need to change password for that database, in order to use it again for BookingWizz, so you'll have to ask hosting provider to explain you where you could change that db password as well.