How can I recursively copy files of a specific pattern into a single flat folder on Windows?

mkdir targetDir
for /r %x in (*.dll, *pdb) do copy "%x" targetDir

@echo off
if %1'==' goto usage
if %2'==' goto usage
if %3'==' goto usage
for /D %%F in (%1*) do xcopy %%F%2 %3 /D /Y
for /D %%F in (%1*.) do call TreeCopy %%F %2 %3
goto end
:usage
@echo Usage: TreeCopy [Source folder] [Search pattern] [Destination folder]
@echo Example: TreeCopy C:ProjectUDI *.xsd C:ProjectUDISOADeployMetadata
:end