If you already own the Steinberg USB eLicenser key with a Cubase 5 license, you simply need the installer, not a cracked version.
Cubase 5 is a 32-bit application. While it runs on a 64-bit version of Windows 10 (via the WoW64 subsystem), it can only access about 4GB of RAM. cubase 5 windows 10 64 bit download verified