Convert m4b to prores

Download and install the latest version of Filestar.
Right click on one or more M4b file(s) on your desktop and select Convert with Filestar.
Type convert to prores in the search box.
Press Convert.

What is the difference between .m4b and .prores?

Name: MPEG-4 Audio Book File; Apple ProRes
Extension: .m4b; .prores
Format: Binary; Binary
Category: Audio; Video
Developer: Apple
Description: It is an audiobook file compressed using .AAC algorithm based on MPEG-4 container format. It is similar to .M4A file but its denoted as an audiobook and supporting audio players can bookmark it.
MIME Type: audio/x-m4a; video/quicktime
Sample: sample.m4b
Wikipedia: .m4b on Wikipedia; .prores on Wikipedia