is that the switch box? if so:
they run only one cable to it, so some of connections are done elsewhere and this is why it does not look exactly as the image in a dimmer manual.
it is still the same though - it is a single pole switch, ground is the bare wire, the remaining two wires go to the switch (or dimmer, see 5a).
you already removed switch so all you have to do is install dimmer:
- connect one of black dimmer wires to black wire in the box,
- connect other black dimmer wire to white wire in the box.
- connect green dimmer wire to the bare wire.
image in step 3 and 5a of dimmer manual shows same thing but slightly differently arranged because they again have illustration with two cables (one is power supply, the other goes to load which is outlet or light). therefore they pass through neutral from one cable to another (white wires with marret). they also connect all grounds together (and the box).
remaining two black wires go to switch (or dimmer).