Unfortunately, it doesn't seem that a way how to convert DASH (Dynamic Adaptive Streaming over HTTP) files to the original exists at the moment, or any other video format for that matter. At best, you will be able to playback it using media player, however without audio track which is not included in DASH file. Except for that dash to wmv conversion appears highly unlikely.
DASH files are meant for watching only (like on Youtube) and not meant for downloading. Try to download the video in other format.Open DASH file Open WMV file