Check How to Use Any Audible Converter on Windows Computer
Run Any Audible Converter on your computer. Click the "Add from local computer" button or "Add from Audible library" button to add audiobooks to the program. You can also drag and drop the audio-book files into the program window directly.
Click on the "Settings" button on the upper right corner to customize the output quality, and output path, set output format as "Original/M4A/M4B/MP3" and select different regions.
Click on the "Convert" button to start converting the audio books to the output format you chose.
After the conversion is completed, you can click the "History" button to find the well-converted files from the local drive. Now you can enjoy them offline.