Thank you for reaching out. My assumption is that you are using GSCopy or GSCopypro, if that is the case, then you could use this format
/IF:ext1,.. :: Include files by mask. Supports * and ? wildcards
Example: GSCOPYPRO c:\source c:\destination /copyall /if:tmp*.doc,log.log (This will only copy files named log.log and files whose names start from tmp and have a .doc extension. This option is not compatible with XF)
if you are referring to GS RichCopy 360, then it is can easily be done by selecting the file in the "file filter option".
So which product you use?