to withdraw pos already converted from usd from the platform
can i send to the exchange to the pos address of the exchange?
Of course. Just make sure you send POS tokens to POS address of your exchange. Don't send to ETH address of your exchange.
Where do you have the tokens at the moment? If you have them on normal ETH address for example on myetherwallet it's all good. But if you have them on exchange and you want to send them from exchange to exchange, then you might gonna have problems. When sending Ethereum or ERC20 tokens from exchange to exchange you should always send from exchange to your own ETH wallet and then finally to new exchange.