You have probably already solved this elsewhere, but the immediate reason for the failure above is that READPDS.PRO could not find the .FMT files; they are in the LABEL/ subdirectory of the data set.
The larger problem is that READPDS.PRO and its ancillary routines are all but useless i.e. they work with some labels but are very sensitive to things like missing keywords, or keywords in a different order than, they expect to see. So even if you put the .FMT files in a location where they could be found you would not be much closer to reading these data (I've tried).
I am working on READPDS for another project but it will take a while and may not fix this problem; I hope you have not been waiting with bated breath for an answer.
Finally, I am a software consultant with a quarter of a century of experience dealing with this kind of stuff and I am pretty sure I could solve your problem quickly, via READPDS or most likely something specific for these data, if you are willing to pay for it.