The error message actually indicates that some files from within the Event Espresso plugin did not get transferred over to the new host. You can reinstall a fresh copy of Event Espresso 3 by following these steps:
1) Download the plugin from your account page. You’ll leave it zipped.
2) Deactivate and delete the Event Espresso plugin from your site’s WordPress dashboard’s plugins page. You will not lose data when you delete the plugin.
3) Upload the new fresh copy of the plugin to your site via Dashboard → Plugins → Add New.
4) Activate the plugin.