Procure-to-pay: find a PO (ME23N) > its goods receipt (MIGO display) > invoice (MIR4) > payment (FBL1N).
Order-to-cash: find a sales order (VA03) > Environment > Document flow > delivery (VL03N) > invoice (VF03) > payment (FBL5N).
Draw both flows on paper with the document numbers.