The sampling rate of the raw signal in the pod5 file can be found within the metadata and extracted using the pod5-inspect tool:
Look for the 'sample_rate' field in the output of 'pod5 inspect debug <path to pod5 file>'. Example:
$ pod5 inspect debug pod5_pass/FAU41813_pass_e6a4b621_0.pod5 | grep sample_rate
sample_rate: 5000