I have taken one of your photo's and pointed arrows where the gold is. You have a couple of flat packs, chisel them off and peal them open and you will see the gold. About 50 will yield almost a gram. The black connectors on the two green cards, that's where the hard disk were plugged into have gold plated pins, crack one open and you will see the gold, there is also the opposite connector on the hard disks themselves, snap those off and cut on the pins and process in Nitric. Also save the gold pins on the hard disks and motherboard.
Rich