AR / AP Ratio Graph | CLEARIFY

I am trying to develop a graph like the attached.  I want to get the accounts receivable days and the accounts payable days in each month and get the ratio between the 2 in power bi.  See attached graph / visual.

The problem I am having is that I cannot get the average days per each month from the out of the box "accounts receivable" or "accounts payable" power bi file.

Is there a way to combine these 2 to develop the ratio?  Is there a way to get the average days / month like the attached graph.  Thank you.