DVs and IVs are similar, but they are stored differently and are modified a bit as IVs, so a direct translation isn't possible. In this case, the current IVs of the Pokémon are completely swept away. After that, three IVs are set to be 31, the maximum value. The exception is with Mew (in Red/Blue/Green/Yellow) and presumably Celebi (in Gold/Silver),
So, there is no way to always determine what value the DV, in this case 15, will be. Every Pokémon will have 3 random 31 IVs unless it is a mythical, where it will have 5 31 IVs.
Source: https://gamefaqs.gamespot.com/gbc/198308-pokemon-gold-version/faqs/75211/3ds-virtual-console-transfer-mechanics
