you'll find some information in these posts
How long was it between the creation of a functioning A-Bomb and the bombing in Japan? Why was Hiroshima and Nagasaki chosen?
TIL that Kokura, Japan was the original target for the 2nd Nuclear Bomb in Japan. However, it was too cloudy to drop it on Kokura and Nagasaki was a secondary target. Why did the Allies believe Kokura was a more valuable military target than Nagasaki?
Why were Hiroshima and Nagasaki the targets of the atomic bombs?
links to posts about alternate targets: Why did the U.S. military decide to drop atomic bombs on Nagasaki and Hiroshima but not on the largest cities like Tokyo?