e=mc^2
The thing is... to do this. You would essentially need an antimatter-matter reaction.
So plutonium is more or less a unneccessary component. You could just plain hydrogen. You simply need mass. Then you need 1:1 ratio so 10 grams of matter + 10 grams of matter.
So the M is double the M.
So basically...
0.02Kilograms * 300,000,000 * 300,000,000 = Joules.
1,800,000,000,000 Kilojoules
Then 1 megaton = 1 million tons.
So 1,800,000,000/1,000,000
So assuming I calculated correctly :)
1,800 megatons
Now you can go with nuclear bomb... but it is ~1% efficient.
Largest nuclear bomb I am familiar with was 50megatons.
So the 100% efficiency of antimatter-matter is amazing.