Change from Windows 7 Enterprise to Windows 10 Pro

Hello everyone,
This is my first post. I have retired from a university and no longer qualify for Windows 7 Enterprise or its upgrade to Windows 10; so I will be purchasing Windows 10 Professional 64 bit. I have read a few posts and am now not sure how to proceed. I would be grateful for any help.
My PC details are:
Windows Enterprise 7 32 bit
Motherboard ASUS P5K Premium Black Pearl
64 bit Intel(R) Core (TM)2 Quad CPU Q9550 : 2.83GHz
DDR2 Memory 4GB (3GB Usable with 32 bit)
2 x PNY Quadro FX1700B Graphics cards
I want to make a Windows 10 Professional 'clean install', formatting a 1TB drive if necessary. The drive will be used for only the OS if possible. Some programs do not give the option to place them anywhere but the OS drive.
I would like to use a USB flash drive to install Windows 10 Professional, which, in the UK, will be supplied by only Amazon at the moment.
The motherboard does not support UEFI. Maybe the firmware can be upgraded.
I have read that I cannot simply insert the USB flash drive into the PC and expect it to install the OS. If that is the case I would be most grateful for a detailed installation procedure.
Thank you. Best Regards, Bill