Some of these parts are generic, and available from any bike shop.
Others are particularly specific, and you may not be able to find them at all, like the plastic covers for gear parts.
Brake lever cover - this is going to be unique to this model and brand of lever, and impossible to find. The unit should work fine without the cover. You could put some tape over to keep dirt and water out.
Brake cable clamp - just use some zip ties to keep the brake cable from touching the wheel
Those aren't axle nuts - instead you need a Quick Release lever like this:
- brake caliper - honestly for a safety-critical part, you're better off buying a new caliper which will come with a pair of pads. You might choose to use the old front caliper as a donor of parts for your existing rear caliper to make one working out of two, and fit the new caliper to the front wheel.
If money permits, you could choose to replace both calipers with the low-end shimano hydraulic brakes which come pre-bled and include levers. Downside to this is that your shifter levers and brake levers are integrated, so now you also need to replace the shifters with a pair of 3x and 8?x thumb shifters.
This is starting to get expensive, and you're not sure if the rest of the transmission works well yet.
You may need to replace the tyres and tubes, saddle, and bar grips depending on how long it has been sitting. These parts can go hard or deteriorate with age specially if the bike is left in the damp to rot, or in sunlight to bake.
BEFORE YOU START spending money, clean the bike and look for damage. It might have been abandoned because there's something fundamentally wrong, like frame damage. Or it could have had the QR skewer stolen and the owner was too lazy to deal with it.
You also need
A stem top cap - to stop you core-sampling your sternum in an accident.
Spacers above and below the stem to cover up the exposed steerer
Maybe new brake and gear inner and outer cables - depends on corrosion levels. The front brake wire outer is definitely wrong - it should be seated in the caliper and in the brake lever on the bars. There should be no inner cable visible between those two points.
Seatpost and saddle - the seatpost has to be sized exactly to the frame's hole, and accurate to a tenth of a millimetre. Specs online suggest its a 30.9mm diameter, but yours might be a different year. Any saddle will do for a test, and as long as you find it comfortable.
Conversely, the grips look good. The bike doesn't appear to be sun-faded. Fork stanchions look clean and undamaged. Tyre tread looks fine - there's almost no wear on the tyres.
I'd be surprised if this bike has done a hundred miles travel in its life. Instead, its been whittled away and uncared for.