You're not "supposed" to download anything with W7 on a modern platform..... that's kind of the point.
Not saying I agree with it, but that's where we are.
W7 should have basic USB2.0 drivers embedded IIRC, while USB3.0/3,1 drivers would need to be installed.
Try connecting a flash drive to a USB2.0 port on the rear of the case - is it detected within Windows?
If so, you'll need to source/download any driver(s) you can locate on another system, hopefully from legit sources. Put those on the flash drive and migrate them over to your new system via USB2.0.
BUT, your best option here is going to be installing Windows 10.
https://www.microsoft.com/en-ca/software-download/windows10
You'll need another system to make a bootable USB, then boot from the flash drive and install W10.
If you don't have a license key for it (assuming you don't), you can skip with "I don't have a product key" and run unactivated until you can pick one up.