Finance question?

Hello, i'm 14 and i'm extremely intrested in coporate finance. I know how to find turnover when refering to inventory and the utilization of that et, but there is a way to find turnover of acount payables. For example a company that has a 30 day billing cycle you can find through acount payables of some sort the actual billing cycle. Going back to the 30 dqay billing cycle if the formula comes out to be a 45 day billing cycle the comapny has a promblem and that calls for alarm. I'm not too sure about this but I read it in a book that vageily described the steps in order to do so.