I have a greencard but I can't find a job in the US so I have never worked there or moved. I just entered with the inmigrant visa snd then received the card in the mail.
You become a permanent resident the moment you enter with your immigrant visa. As a permanent resident, you can move wherever you want, whenever you want.
(If you're talking about moving outside the US, there's no restriction on the timing of this move, but there are restrictions on the length of time you may remain out of the country without losing your permanent resident status. You can apply for permission to exceed these limits.)