can someone give me a example of the syntax for robocopy to copy from one drive/directory to another drive/directory , I need to just backup a directory every night, nothing fancy, and only need to ...

I think you are right. The /MIR option says that /MIR is equivalent to /E and /PURGE, and /PURGE is supposed to "delete dest files/dirs that no longer exist in source". I have no idea why it isn't ...