CD Drive not recognized reinstalling windows - Latitude E7250

Team

I'm trying to reinstall windows 7 64bit off the Dell CD. I have an external DVD drive plugged in as this laptop doesn't come with a drive.

I get part way through and it asks for drivers for the CD/DVD drive - but there are none..

After 12 hours of googling I've found Windows 7 installation media does not have support for USB3 ports - this laptop only ahs USB3.. How the *** do I get around this?

"Windows 7 install media doesn’t have native support for USB3.0"

I've downloaded the Dell 7250 CAB and extracted it to the C Drive of the laptop I'm trying to re-install to, and when it scans for suitable drivers, it doesn't find anything compatible to allow the DVD drive to be seen.

What do I do? How do I get the laptop to recognize the external drive?

Thanks