I am installing Debian 10 on asus zenbook ux333f from USB and during the installation it says that my hardware needs non-free firmware files and that those can be loaded from USB. The files I need are iwlwifi-9000-pu-b0-jf-b0-38.ucode iwlwifi-9000-pu-b0-jf-b0-37.ucode iwlwifi-9000-pu-b0-jf-b0-36.ucode iwlwifi-9000-pu-b0-jf-b0-35.ucode iwlwifi-9000-pu-b0-jf-b0-34.ucode iwlwifi-9000-pu-b0-jf-b0-33.ucode iwlwifi-9000-pu-b0-jf-b0-32.ucode iwlwifi-9000-pu-b0-jf-b0-31.ucode iwlwifi-9000-pu-b0-jf-b0-30.ucode. I have downloaded on another USB a firmware as recomended here https://wiki.debian.org/Firmware but is seems that debian does not see those firmware.
The page[1] you listed mentions that sometimes there might be issues detecting the firmware. If you are not comfortable doing manual mounts, and other manual troubleshooting actions, you can always try an image with firmware already present.
From the same page[1]:
Alternatively, you can use one of the parallel installer image builds that also include all the non-free firmware packages directly. We have "netinst" CD images and also DVD installer images - see http://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/
Assuming you are installing a "default" 64bit image, you can maybe use a netinst image with the firmware[2].
In case you are not familiar with netinst images, here a small description of what they are:
The netinst CD here is a small CD image that contains just the core Debian installer code and a small core set of text-mode programs (known as "standard" in Debian). To install a desktop or other common software, you'll also need either an Internet connection or some other Debian CD/DVD images.
I usually install all my Debian boxes from a netinst image and then download all the required packages during installation depending on the choices of the install itself.
Please note that if you do not have internet access during the installation this option can be bothersome, or even not practical.
[1] https://wiki.debian.org/Firmware
[2] http://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/current/amd64/iso-cd/