Bombs dropped on Japan were in the 10-20 kiloton range. Very Big cold war era H-bombs were up.to about 20 megatons, so about 1000 X. Contemporary missile carried MIRV bombs run around 150 kilotons, about 10 X. Militarily speaking, more, smaller bombs are more useful.than a few big bombs.

In about 1975 I saw an estimate that about 400 medium size bombs would be required to completely destroy everything and everyone in the Soviet Union. (This estimate only considered "prompt" deaths and destruction. No consideration was given to long-term radioactive damage or starvation. Yes, it was a fun time to grow up, why do you ask?)