I don't know what was the conversation between the two of you and the guy made you believe to transfer that kind of amount easily. Sorry for your loss but you can't get your USDT once they have been sent to an address which you don't control.

Even the police will have a hard time tracking and tracing the guy since its fairly easy to use a different address. Maybe next time don't try to send an amount that big or maybe use an escrow if you are doing an online transaction with somebody else.