Convert cURL to Postman REST Call

The content-type is not application/json, it's application/x-www-form-urlencoded. What you need to do is in the body tab, select application/x-www-form-urlencoded. The content-type header will automatically be set for you. The just start adding the key/value pairs (the --data-urlencoded arguments)

UPDATE

Unrelated, but for those looking for a way to post JSON (which is very common), you would use the "raw" radio button and then you would manually type in the JSON to the window they provide. Also you would set the Content-Type header to application/json.