You cannot restore a classical backup of one databas type to another.
You need to use export and import features. Because the structure, format and language of two database and its related tools differs.
There DB specific tools for migrating, exporting and importing data between two databases - what is called as a data movemen, a tasks for DBAs.
However, with SAP you have native and generic tools and methods for migrating databases and operating system. One should use them starting from OS/DB migration check to successful migration of production system.
backup/restore detach/attach etc.. These database specific methods are possible cases with when your target OS/DB remains the same.
Regards,