Wiring for 220 plug

Just moved and the ground wire worked lose, however there is a green wire than nis also disconnected. I have been told that the green wire remains unusede and all I have to do is reconnect the ground?

Need more details.
Is it 3 or 4 wire?
Does the unit have a line cord or is it hard wired?
What is the plug type at the new house?
Have you changed the line cord?
How do you know that the ground wire came loose as this is usually inside the unit?

Plus anything else you think may be relevant!!