Thanks for putting me on the correct path.
I checked which version of Debian PureOS uses, Buster.
cat /etc/debian_version
It took a while to find the correct file, but I found it at
https://packages.debian.org/buster/firmware-iwlwifi
When you go to download a file from packages.debian.org, check it has what you need inside.
dpkg-deb -x *.deb /tmp/deb-extracted/
To install the correct downloaded deb file.
sudo dpkg -i firmware-iwlwifi_20190114-2_all.deb
To activate the wifi adapter, restart your PC or run
sudo modprobe -r iwlwifi && sudo modprobe iwlwifi
The wifi icon does not appear in the system tray (I’m running off the live disk, so cannot restart), but it can be used in the settings panel.