You need to ensure that you have a policy which covers trekking to 5,610m, but it does not need to cover technical climbing. You're advised to take out insurance to cover potential events that might cause you to cancel your trip. You should bring with you a copy of your policy and also a photocopy of your passport, and to keep it separate to your own documents in the unlikely event that you lose your passport. I have often used the British Mountaineering Council insurance for my own personal expeditions, but many other insurance companies offer policies suitable for Mount Damavand: https://www.thebmc.co.uk/insurance