There are a lot of ways to say it.
Ada-nuh
Ada-nah
But the one I think is the most common is:
Ad-a-nuh
I think it's because it's a name that's often used as a last name.
I'm from the Philippines, and the most common way to pronounce it is Ad-a-nuh.
I have heard it pronounced "Ada-nah" and "Ada-nuh".
I think the "Ada-nah" pronunciation is the more common one.