PO Created by name in WOrk flow

Hello Team,

I am doing a work flow development -

Where if a PO is changed by other users - the person who created the PO should get a notification ..

I got some reference - did accrodingly... But I am not getting person / details of PO created by in my work flow.. hence emails are not triggering.

Please refer my screen shots in the below and let me know if you need any further details.

I need to get PO changed details.

Thanks,

SK