No, it is not possible to connect a FireWire interface to your computer's USB port via a FireWire to USB adapter, since this connection is not sufficient to run a FireWire audio interface.
If your computer does not have a built-in FireWire port, you should check if it has a PCI or PCIe slot (desktop computer), or a PCMCIA or ExpressCard slot (laptop computer).
This article explains which cards work the best with Focusrite FireWire interfaces:
For information on connecting FireWire devices to Thunderbolt 3 (Type C) ports, please see this article.
For Saffire compatibility on Windows 10, please see this article: