Hopefully this is something you discussed with your freelancer before you hired them. There are implied contracts built into Upwork's model.
But if you Google "free nda forms", you'll find plenty of forms online that can be downloaded and used. Many here have suggested that it's best to work with someone local to whereever you're located, as holding someone to a signed document could be problematic if they're halfway around the world.
I've flagged your post - hopefully a forum mod will come along with more knowledge than I have about this.
Unfortunately we do not provide NDA templates. In addition to Virginia advice:
Upon Freelancer’s receipt of full payment from Client, the Work Product, including without limitation all Intellectual Property Rights in the Work Product, will be the sole and exclusive property of Client, and Client will be deemed to be the author thereof.
To learn more about this, check out our Therms of Service under 8.6 Intellectual Property Rights.