Database issue with MS VC++ 6.0 code

My existing application code is in VC++ 1.5 and used Quadbase proprietory database ( a 16 bit database).
I need to convert this application to VC++ 6.0 and correspondingly need to change the database to a 32 bit one.
Which database should I choose so that the code changes will be minimum ? What sort of VC++ 6.0 code do I write to access the new database ?