FbxConverter 12.1 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free Mac app is a product of Autodesk Inc.
Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. The most popular version of the tool is 12.1. FbxConverter for Mac lies within Design & Photo Tools, more precisely 3D Modeling.
From the developer:
Transfer files from one file format to another more quickly and easily with the Autodesk FBX Converter asset exchange technology. FBX Converter utility enables you to convert OBJ, DXF, DAE, and 3DS files to or from multiple versions of the FBX format.
You may want to check out more software for Mac, such as Realsoft3D, formZ RenderZone Plus or FRS Coloring Book Volume 2, which might be related to FbxConverter.