Yokohama is a famous Japanese city; at 3.6 million, it is the largest incorporated city in Japan.
The two other names are outmoded. “Peiping” is an archaic Anglicization of the capital city of China, known later as Peking and nowadays as Beijing.
Bradbury’s use of “the Celebes” is a misnomer, because it is only one of four large Indonesian islands, as well as archaic. Celebes was the name of a large island between Borneo and the Maluku Islands (in the Southeastern Pacific, north of Australia and east of Indonesia) known today as Sulawesi.