Will I need to make sure I buy a USB of Windows 11?
Most likely you would pay for a license from a reputable site: Microsoft direct, maybe Newegg. I'd probably use Microsoft direct to avoid any possible Newegg snares regarding downloading or email.
Then you would make the installer yourself using your own USB stick via Microsoft's "Media Creation Tool". Not sure, but it may need to be 8 GB in size or larger?
Then boot the PC from that USB stick and hope.
Not sure if it is possible to buy a "USB of Windows 11", but that would not be the common method even if available.