iExplorer and Adapter are both our applications, yes. Adapter is freeware (100% free), and iExplorer is shareware (some free, some paid):
Do you mean voicemails (phone messages)? Voicemails are in the AMR format which is a format chosen by phone companies awhile ago, but Voice Memos (recorded in iOS Voice Memos app are in the M4A format).
Here are some articles to cover both, but I assume you mean voicemail, and the first one has instructions on how to convert the file in Adapter:
How to transfer iPhone voicemails to computer
Tutorial: How to export and save iPhone voicemail to computer
How to transfer iPhone voice memos to computer
Tutorial: How to copy iPhone voice memos to computer