Robocopy /mir and keeps destination 2 file Unchange.

Hello Team,

I am using Robocopy to copy paste files from Production server to Staging server , i want to move all files from production to staging  using mirror excluded 2 config file, in this i want Destination file should not delete old 2 config file.

Below code :

robocopy <source file>  <destination file> /MIR /XF Web.config Key.config

In above code, source file exclude "Web.config" and "key.config" thats right 
but 

in destination, files become deleted "i don't want to delete want to kept as it is(old 2 config file)". 

Thanks for helps.

Regards,
Yogesh Jumani