In order to compile the tools sdds2opal and opal2sdds you have to download the source code of SDDS version 3.4
at https://www.aps.anl.gov/Accelerator-Operations-Physics/Software#SDDS%20Source .
Unpack the sources, change to the directory epics/extensions/src/ and then upack the archive SDDSCMakeLists.tar.gz
in this directory. Finally apply the patch SDDS.patch with the command
$ patch -p1 < /path/to/patch/SDDS.patch
Now you can use cmake to compile and install the SDDS library.

Comment from Christof:
These two programs (not scripts) export particle positions and momenta from HDF5 files to SDDS and from SDDS to ASCII (which then can be used to as FROMFILE distribution)