Log into Upwork client-size webpage.
Upwork -> Jobs -> All Contracts
You will see a list of past contracts. (Only closed contracts have feedback, so that's all you care about.)
Click on a freelancer's name
Cick on "Terms & Settings"
There is the feedback... From you to the freelancer, from the freelancer to you, including star-averages and text feedback comments.
In addition to what Preston said, if you want to see *all* your feedback in one place, you need to view one of your job posts (either current or previously closed is fine). Scroll to the bottom of the post and you'll see all your past feedback from past closed contracts.
(As an aside: you are an Upwork *client* and the people you have hired are *freelancers*. This is not a platform where you have an employer/employee relationship, generally.)