PB (packed model) is the model format used by Atlus in Shin Megami Tensei III: Nocturne, the Digital Devil Saga duology and the Raidou Kuzunoha games. Along with PB you may also find some other model formats, such as:
PB 3DS MAX importer
TGE created a maxscript that's intended to be used with Autodesk 3DS MAX. It supports importing PB, MB meshes, rigging, materials. You can get it here.
Skinning or texturing information may not always be perfectly retained and models may require manual tweaking.
DDS3-Model-Studio (or DDS3ModelConverter) is a tool for converting skinned models to formats such as DAE, OBJ, FBX.
Rigging and mesh/texture conversion is currently possible. You can download the latest build here or get a version that includes DniweTamp's windows .bat script for mass converting of PB and MB models to all three formats, DAE, OBJ and FBX, here.