Animation
Unturned’s character rig is terrible – so using existing animations is recommended for your sanity.
Export
Ensure scene unit system is metric with unit scale set to 1.0 and length set to meters.
Select the Skeleton node.
File > Export > FBX
Selected Objects: True
Apply Scale: FBX Units Scale
Add Leaf Bones: False
Primary Bone Axis: +X
Secondary Bone Axis: -Y
Note that the Item.prefab from Unity is attached to the left or right hook with a local rotation of (0, 0, 90).