STDF is a file format developed by Teradyne. It is in a binary format. There are libraries available in R and Python to read the files, however because of the complexity of the format, the reading of a single STDF file, typically will end up resulting multiple raw data and summary data files.
There is an STDF to ATDF utility provided by Teradyne, that converts the STDF file to an ASCII format, which is human readable. But it also remains a complex data structure that contains multiple data formats for the various record types in the file.
My suggestion is that you contact one of the commercial companies that provide STDF to JMP addins or Adsurgo, an other provider of JMP addons.
Jim