The search term you need is 'data pump'. For example, check out Clever Components - Interbase DataPump

 

. It's free and can connect to both Interbase/Firebird and any database that has an ADO/ODBC driver, including MSSQL and Oracle. You'll need a working server to connect to, but if the application is functional right now, you probably have that (unless it uses Firebird Embedded). Otherwise you need to look into setting up a Firebird server with the existing database.

If you don't want to pump data directly from one database into the other, and would prefer a readable intermediate step, you could export tables one by one to CSV or XML. For that, have a look over here: How to export data from database and import into another?

 

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