Sorry but I can't make heads or tails of the diagram.
If you've only got one north and one south pole ("two pole") it will be 3000 RPM for 50 Hz, 3600 RPM for 60 Hz. If you've got two each it will be half that.
A lot of inexpensive direct-drive alternators do run the engine at 3600 RPM and use a two-pole alternator. It cuts the life of the engine compared to a four-pole design but simplifies the alternator.