How do I identify a what kind of power connector for AC mains is on a product?
Look for IEC320 reference tables, the connector should match one of the international standards. Once you identify the connector you can search for it. If not, it is a custom cable and the manufacturer will need to be contacted.

The first edition of IEC 320 (later renumbered IEC 60320) was
published in 1970.
Source: Wikipedia

This is what a table looks like

Source: https://www.stayonline.com/reference-iec320.aspx
Edit:
Another good resource https://www.plugsocketmuseum.nl/ApplConn_overview.html