Dear Sir,
I am a professional streaming developer and I can help your team integrating stream API into your website.
Here is the answer to your question:
In steam, in the top left corner hover your mouse over your name, go to inventory, trade offers and to the right somewhere it should say ''who can send me trade offers'' click that and then scroll down and you should see the link you need.
If you would like to have an online discussion with me, please do share your SkypeID and we can discuss this further.
Please let me know if you've any kind of queries and questions, I'm all here to help you out.
Many Thanks,