Problem with withdrawal from steemit.com to poloniex.Need help

Hi I transferred 2 days ago 91 steem from steemit.com to poloniex.

address and memo is correct,i triple checked,i can see it in my history and I can also see it in poloniex's history here on steemit.

I created a ticket at poloniex.com and they are asking me for a TX ID of the transaction?

what is that?where can I find it?

please help!