short script to read and create matching directories (not sure how to word this)

i need a z:\music\: dir *flac* to listing of directories have "flac" in them... (they named artist - album [flac])

and list of directories, create new matching directories, replace [flac] part [mp3]

so i'll end with 

artist - album [flac] 

and

artist - album [mp3] 

dir z:\music | ? {$_.psiscontainer -and $_.name -match "flac"} | md -path {$_.pspath -replace "flac","mp3"}

Windows Server  >  Windows PowerShell