It will load wma files if that's what you have, just set it at the top of the script:

file_type = ".wma" --{".wma",".wav",".m4a",".aiff",".flac",".mp3",".wv",".ogg"}

Reaper can batch convert your files to any compatible format you like then set the type in the script else just use wma.
There is also a script to create the reapeak files for whatever media type you are using so the tracks load instantly.