HDF is a file format library (as XML format for example). HDF5 is the actual version of the HDF format and can be imported in FlexPro 2017 as well as in FlexPro 2019. Export to h5 file (HDF format) is also supported by both versions.
Head Acoustic use the HDF file format library to create their data file with some specifications. These files can also be directly imported in FlexPro.
If you would like us to test if your files can be imported in FlexPro, you can send them to firstname.lastname@example.org. If the files are too big for mail transfer, we can give you an access to our upload platform.