Azure Notification hub needs Cloud Messaging API(Legacy) key to connect with FCM, legacy will be deprecated soon.
So how can we migrate Cloud Messaging API(Legacy) to FCMv1.
Web API key isn't useful for Azure Notification Hub as if you try insert this key into the API key entry for a hub
Question: What do I have to paste into Azure's push notifications settings where my FCM key was used before?

Create a firebase project in google firebase.
Then navigate to
settings > cloud messagingthen you can find Cloud Messaging API (Legacy) key.Add the server key in Azure notification hub -
Settings > Google (GCM/FCM)and click on save.I have an application which can communicate with ANH that can receive the notification which I sent and from ANH to (GCM/FCM).