Believe in power of prayer. Will it work for dealing with loss?

Yes. Grieving has been a part of life since the begining of time. All religions have developed strategies for dealing with loss. The process of connecting to a higher power and more importantly to reconnect with those who are still alive are a part of most religious ceremonies. But if grief becomes immobilizing and prolonged seek professional help.
Yes. Spiritual pracitces can be deeply meaningful and helpful in dealing with difficult situations.
Self- care. I also believe in the power of prayer. Prayer doesn't make all of your problems go away & doesn't remove the necessity of grieving. But prayer can be a salve that soothes your suffering. It may bring hope when hopeless. It may comfort your anguish. It may combat the sense of being utterly powerless. It invites the assistance of a higher power. It is often beneficial when working through loss.
Self-contradiction. Right after you say you believe in the power of prayer, you question the power of prayer. If you believe in the power of prayer for anything, wouldn't you believe in it for everything? If you don't know if prayer will work for dealIng with loss, then what does it work for? If prayer for you means to a Supreme Being, why would you trust that other people know that Being's ways any better than you?