one of our suppliers would like us to supply an excel sheet containing our PO. how can i generate that?

Create a saved search. Add Mainline Name to Results. Go to Email subtab and chech Schedule checkbox. Select Mainline Name in the Receipt from Fields. Go to Schedule and select time and frequency, then CSV

Assuming CSV is acceptable. If they need Excel you will need to script it. Sheet.js works well in SuiteScript

thank you