I am not sure what you mean by "relevant PO data in warehouse Module", an example would help.
In SARA you can see an icon for Network graphic, this gives you an indication about the sequence of archiving for an archiving object. You will see what object you have to archive prior to your entered object.
MM_EKKO has no such dependencies pre-defined by SAP. What you see in the Network graphic is subject to customizing and should be amended based on your processes. But it will have no technical influence, it is just for information.
However, there are dependencies, dependent on your process design. E.g. if you are doing Stock transfer orders with delivery or third party orders.
To know such dependencies you need experts in your project team, otherwise it can happen that you archive data which is needed to complete a process. you need to test such integration and may need to restrict archiving via user exits.
A good way to learn is from errors made by others, so the source for such information are usually SCN discussions and OSS notes.
The cross connected data can be seen via ALO1 transaction