You can find a number of MoCap files at www.turbosquid.com. I noted there are several freebie files that are in fbx format that you'll need to convert. Of course, they also have a lot of mocap for purchase. The quality and cost of the files varies widely, though.

You can find pre-made motion files from a number of sources such as www.daz3d.com. However, you might benefit from working through the nice walk designer tutorial here: http://www.daz3d.com/support/tutorial/tutorial.php?id=922

TheDoctor