Remove the ip address from the user.
net use r: \\192.168.1.111\files /user:admin
I would recommend that you copy the files from R to S and then verify that they were all transferred without error. Then go back and delete the files from R:
robocopy R:\ S:\ /e
You may also want to use the /l switch which will tell robocopy to just list the files that it would copy without actually copying any data.