How to do log in test using Jmeter for web app which uses Cognito?

While logging in, web app uses Amazon Cognito and gets tokens to authenticate. The problem is, the tokens expire every hour and the test works properly only for an hour. The tokens aren't coming in response in any previous HTTP request so that I could make a correlation. My question is how to get the tokens? I know there is an endpoint described here: https://docs.amazonaws.cn/en_us/cognito/latest/developerguide/token-endpoint.html but I still don't know how to get the parameters which I have to put in the request.