Working out RPM from Hertz

Apologies I am the newest of newbies and this is post 1.

I have recently acquired an old AXYZ 6010 which seem to be in reasonable condition despite its age. At some point it has been converted to a Mach 3 controller and it has had various upgrades and 'downgrades' in the distant past. The previous owner had some problem with the machine and the spindle speed is not controlled by Mach3. It is simply controlled by the manual controls on the VFD. Effectively he had a software issue, could not sort it out and converted it to this manual setup. Upon asking him about spindle speed he said 'yeah you can change it but I never bother'. Eek.

The VFD is a TBwoods E-trac X2C AC inverter that displays the Hertz. The motor is a VS 60.11-2 7 hp Perske 3phase. I have read on the forum how to work out the RPM from the hertz but I don't know how many poles this motor has.

Can someone advice please?

Cheers