I purchased an old electric dryer to hold me over until I can have a gas line installed in my laundry room and am in the process of converting it from a 3-prong to a 4-prong plug. According to the warning the ground and neutral should be bonded. The problem is that there doesn't seem to be a white grounding wire. What do I do with the ground to wire this thing up safely?
The metal Z-strap is the bonding link
The N-G bonding link in your dryer is quite plainly visible in the second photo you posted; it's simply that your dryer used a metal Z-strap from the neutral screw on the terminal block to a nearby chassis grounding screw as the link, instead of using a wire with ring terminals on each end.
So, to convert this dryer to 4-wire, you'll need to replace the cord with a 4-wire cord, remove the Z-strap, and fit the ground wire from the cord to the grounding screw (on the right side of the cord wiring compartment) the Z-strap was grounded to. Neutral goes in the middle, and the two hots go on the ends of the terminal block.
The middle nut on the terminal board is the neutral. You can see the two white wires connected to it. You and also see the jumper going from the neutral to the housing. If you're going to go to a four prong plug, you will need a four wire cable and plug. The black and red wires from the new cable will go to the two outside nuts, the white wire will go to the middle nut and you want to remove the jumper. Then the green wire from the new cable will go to the screw in the housing, grounding it.