H.264 MP4 is the most supported video format now. You can play it on a PC, Mac, iPhone, Android and most smart TV natively.
If you would like simply extract the audio from the video, just put the video on timeline and then entering the "Produce" tab. In Produce tab, choose Standard 2D->Audio file (the notes icon) and pick M4A as the audio format. The audio codec is AAC and most devices should support the format. PowerDirector no longer supports produce a MP3 audio anymore.