There is support for accessing your local file system coming to Postman soon. That would be in a very specific way though by connecting a Workspace to a local project on your machine.
Currently, Postman doesn’t have access to your full local file system to be able retrieve data in the way that I believe your trying to do this here. There are a few different ways that it can reference local files, like with the form-data payload file and a CSV/JSON datafile used with the Collection Runner and Monitors.