If your Blazer has a distributor cap, it's usually located on top of the distributor, which is situated near the center of the engine, somewhat towards the front. It'll be a fairly easily visible, roughly cylindrical component with several wires connected to it. However, as noted, this is less likely than finding a coil-near-plug system.
To be certain, you should:
1. Check your owner's manual: This will definitively state what type of ignition system your vehicle uses.
2. Look at the engine: If you can't find a distributor, it's likely a CNP system. You'll see individual ignition coils mounted directly to the spark plugs or very close to them.
In short, it's more probable you won't find a distributor cap than find one.
