If you're someone who gets motion sickness well riding in a car or public transport such as the bus or train, then motion sickness will effect you in a helicopter.
Sufferers of motion sickness should not be taking a helicopter ride, so its important to let the company know so they can advice such as providing sick bags.
If you do decide to fly and you're allowed to proceed; then a helicopter service in the know, will know not to seat you in a seat that is facing backwards.
Be sure to mention this to the helicopter service so you are seated facing forwards, not back.