You do need to have the ATF drained and refilled every 3 years or 30k miles and it has to be refilled with only the Honda ATF. You cannot use a generic ATF with “additives” that so many transmission chains like to use, and Honda specifically recommends against doing a “flush”.
The ATF that is recommended in your owners manual is Z1. They no longer stock that, they have a newer ATF and it will actually help your transmission shift better in cold weather. It mixes with the the Z1 and even when mixed, it still improves the performance of the transmission.
Your transmission holds about 6 quarts of ATF, but only about 2.5 will drain out at a time. The rest is trapped in the transmission. If you have been doing the drain and refill on schedule, then that is all that is needed for the transmission to last the life of the vehicle.
If you have not been keeping to the schedule, you have four options. One is to do nothing and just replace the transmission when it gives out. This would probably be the best option if you have over 180k miles on it.
You can do a simple drain and fill and do it every 30k miles from now on and get a little more life out of the transmission. If you have less than 120k miles on the vehicle, this is a good option. If you have less than 90K, this would be the best option IMO.
You can also do one of the following, four drain and fills about a month apart or a fluid exchange machine. A fluid exchange machine is different than a flush as it doesn’t pump any ATF through the transmission. It lets the transmissions pumps do the work. But insist that they drain and refill before hooking up the machine. Otherwise they are adding fresh fluid to the contaminated fluid in the sump. They will never get all the old out that way, no matter what they tell you or what the video they show you says.