“Prebellum” and “antebellum” are both ways of saying “before the war” in Latin. There is nothing wrong with the former term, other than its relative rarity. If you search you can find “prebellum” being used (in the same sense as “antebellum”, e.g. with reference to the US South before the 1860s) in various academic papers, newspaper articles, etc.

https://www.google.com/search?q=%22prebellum%22&tbm=bks

https://scholar.google.com/scholar?q=prebellum