Copying voicemail greetings from FreePBX 10 to 13


I have an old system that I am upgrading. I am installing, in a new box, the latest distro.
I would like to know what I have to convert the audio from the Freepbx 10 (FreePBX to the FreePBX 13 distro installation in order for the voicemail greetings (and IVR welcome messages, etc) to be copied onto the new installation and work. I have locations and I have tried it directly but it does not seem to recognize that there are any audio files in there. I am assuming there needs to be a bit of conversion in the audio files.

If I am way off my mark, please let me know!