Replace ignition coils with spark plug?

The ignition coils don't need to be replaced. You can be sure that Toyota would recommend their replacement if it was even vaguely justified so they could generate more service income for the dealerships. Prius's are very low maintenance cars, don't start looking for trouble. My 2018 doesn't call for a spark plug replacement until 110,000 miles. I'm not sure if your older model needs to have the plugs replaced sooner.

If you aren't experienced with replacing spark plugs, I strongly recommend that you get a torque wrench to do the job to avoid damaging the threads.

 

There really isn't a need to do either. They are iridium plugs and can easily last more than 150K miles. I didn't run into ignition coil issues until around 250K+ miles. The engine will intermittently miss under load. At that point, replace them all instead of trying to locate the intermittent coil - other will say. Just replace the bad one. If you got 250K miles out of the originals, I'd say it's time to replace them all in one shot - to avoid another one going out in an in-opportune time.

Just my 2-cents.....