Your image shows two messages:
There is a message
ERROR:root:Couldn't open wallet.dat/main
It suggests you should close Bitcoin if it is already running. I would use Windows’ task-manager to see if bitcoin-qt, bitcoind etc are running (Ctrl+Alt+Del in Windows-10 should bring up a menu from which you can select
task-manager). You can close those processes from task manager if necessary.
Since your screenshot shows a second attempt without this error, it looks like you shut down Botcoin-qt OK and the command completed OK.
WARNING:root:pycrypto or libssl not found, decryption may be slow
This is just a warning, it doesn’t mean that the command won’t work, just that it may take longer than normal.
The message suggests pywallet will use slow internal cryptographic functions if it doesn’t have access to a fast external library of cryptographic functions.
wallet.txt file should show you the information you wanted to extract.