How to select files of one format, across many folders, for conversion?

[barnw]

I have tried with the Add files - when I select *.wma for the file name, or wma from the supported extensions, I do not get a list of wma files.  If I try to select folder (really more appropriate for me, as I want to convert all wma files in my music tree), it adds All files, very time-consuming and unnecessary - don't see a way to just add .wma files from across the folders.  So, how to do?