cf-download | Cloud Foundry cli plugin for downloading your application

You don't need any plugins, you can use scp or sftp.

The documentation is here, but this is a summary:

1. cf login and cf target
2. cf curl /v2/info | jq .app_ssh_endpoint this is your SSH host
3. cf ssh-code then copy the value, this is your password
4. cf app app-name --guid this is part of your user name
5. sftp -P 2222 cf:/@, when prompted for a password, enter the passcode you copied in step #3.

Similarly, for scp you can run scp -P 2222 -oUser=cf:/ my-local-file.json :my-remote-file.json.

Hope that helps!