I want to move to another state, and my total migration power is 3.3 m, which is costing me 2 migration..

Is hero power only shown to you when you migrate? I believe the only way to reduce any effect of heroes would be to delete some of them as you cannot remove skills. Deleting is done by splitting them. Go to each hero in the hero menu and at the bottom tap the skill icon on the right. Then at the top left next to the picture will be a small face icon with an X. You will only see this if the hero is not currently being used (stationed). Tap this icon to split the hero and get some of the medals etc back that you have used on it. Once they are gone though you will need to recruit them again and start unlocking their skills from scratch.

I am not sure how effective this will be for your migration though as I believe the game keeps a track of you average power rating over time so suddenly dropping a lot of power may not have as much of an effect as you want, but I have not tried this myself. If you do try it please let us know if it helped.