Yes you need to plug the HDD into the ps4, plug another drive in too, use GoldHEN and pkg extractor to copy the pkgs from the 9.00 drive to the empty one.
Then on a pc you need to backport the games.
Did you ask this person if they could set it up for 5.05? They probably could have put games...
My assumption for this scenario is that you’ll need the latest GoldHEN for 5.05 that supports extended storage, and you’ll need to use FTP or a PKG dumping payload/brew to get the 9.xx FPKGS and patch/remarry them with backport patches.
If that’s more hassle than it’s worth: update to 9.00 to...
Doesn’t 18.x require the modded fusee by unicornman to work properly?
I updated mine from 16.0.0 to 18.0.1 yesterday with daybreak, and it works fine using latest AMS, with the fusee bin here...