Answer
∴Nickel(II) Nitrate Hexahydrate molecular formula will be $Ni(NO_3)_2 ⋅ 6H_2 O$
Work Step by Step
nickel(II) is having a charge of +2
Nitrate is having a charge of -2
Hexahydrate is having total 6 molecules of water
∴Nickel(II) Nitrate Hexahydrate molecular formula will be $Ni(NO_3)_2 ⋅ 6H_2 O$