After you transfered ur case to Poland, now you need to wait until ur case number is going to change to WRW instead of MOS.
How do you know it happened?
Your MOSxxxxxxx number will stop working, when you check your case status at nvc (https://ceac.state.gov/CEACStatTracker/Status.aspx )
How do you find out your new NVC number?
You have to call NVC/use ask nvc site and request ur new NVC number
Phone: +16033340700 or +16033340888
Ask NVC form: https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/ask-nvc.html
Please note that waiting time on hold is ~ 2h
And the ask NVC form is gonna be answered 7 days to a month