We have Informatica cloud in our organisation as well as Salesforce Marketing Cloud. I have seen several articles referencing a Marketing Cloud connector in Informatica but cannot find any such connector in the tool. Has this connector been retired?
This documentation explains a bit more on Informatica's connector. It is setup similar to other 3rd party integrations that leverage the Marketing Cloud API. E.g. ReturnPath, etc.
This requires your Marketing Cloud admin to create an Installed Package in Setup > Apps > Installed Packages.
Once the Installed Package is created you will provide the client id/secret and other credentials to allow Informatica to connect to your Marketing Cloud instance.