Cypress is usually used to perform e2e tests. Which means that you typically don’t want to replace or mock modules in your app.
Sometimes, the need to mock some of the modules generated because you want to mock some network requests, so that the test data does not mess up your production environment. For example, you don’t want your test data to end up in your production database.
If you also have similar requirement, then I would suggest to use a proxy to capture and modify the network requests that you want to mock. As I am not using cypress myself, I can only provide this resource which shows the example of proxying network request: https://blog.bitsrc.io/mocking-http-calls-in-cypress-end-to-end-tests-fa2e6b7caaf7
Additional resource: https://playwright.dev/docs/network (with playwright, but elaborates the concept bit more directly IMO).
In case your mocking need is different than what I have described here, you might be better served with unit tests instead of e2e tests.