You wouldn't use VB to convert a database from Access to Oracle. I believe Oracle has a conversion tool that allows you to migrate your database objects (tables, queries) to Oracle via a wizard.
Oracle doesn't use the same data types as Access and the Oracle SQL dialect (PLSQL) is quite different from the syntax you'd use with Access.
As far as your front-end app, you would need to change your connection string and most of the data sources of your recordsets should be stored procedures instead of queries. With ADO as your data access method, this is pretty straight forward.
The wisest people are those who are smart enough to realize they don't know it all.