If you're looking for the USB COM port driver for 64-bit Windows, try
this package from ST Microelectronics. You'll have to create an account in order to download it.
Note that installing the downloaded package doesn't install the drivers, it just copies the installer(s) into "C:\Program Files (x86)\STMicroelectronics\Software\Virtual comport driver\". You then need to run the appropriate installer from there. The 64-bit Win8 driver seems to work for Windows 10.