Complex sentence: In August of that year, Kay-Bee's parent company Melville Corporation purchased Circus World, shortly after which most Circus World stores were converted to Kay-Bee Toys (later renamed KB Toys).
Split into simpler sentences: In August of that year, Kay-Bee's parent company Melville Corporation purchased Circus World. Shortly after the purchase, most Circus World stores were converted to Kay-Bee Toys (later renamed KB Toys).