Most Drivers are more or less compatible with DirectX9, unless specific DX9 capabilities are required, which no 3dfx Driver has.

So do you have any specific Problems with your existing Driver under DirectX9 ? Any specific Game or application, and which OS are you using ?

The Name 3dfx16v3 is merely the name of the Core File, you'll have to look up its Version in order to tell at least somewhat which 3dfx Driver Generation you have installed.

What OS are you running ?
On Win2000/XP I recommend the SFFT drivers, up to date is Alpha 22. Get them on www.3dfxzone.it, they offer DirectX-8 features.