instruction to boot PC from USB

Hello,

I have  done  all the diskpart commands as listed out there all over the place

but that will not make the usb key bootable (bootmgr missing)   I want the usb key to boot just like an old floppy would (Format /s)

I don't want to install windows 7  just boot from the use b key and then be able to run "windows defender offline" or some of the other malware tools

thanks