I am using the url base url of my org to connect with postman ,which is https://curious-moose-190477-dev-ed.my.salesforce.com and getting the error. Please find the attached image.
You have to create a connected app in salesforce to authorize postman. You need to ensure you add https://www.getpostman.com/oauth2/callback to the callback URL list
Postman has built-in OAuth-base authorization. In Postman, click on the Authorization tab and select "OAuth 2.0".Click on Get New Access Token to launch the OAuth dialog. Use the following values:
Token Name: (Any friendly, descriptive name) Auth URL: https://login.salesforce.com/services/oauth2/authorize Access Token URL: https://login.salesforce.com/services/oauth2/token Client ID: (the consumer key from your connected app) Client Secret: (the consumer secret from your connected app) Scope: (you can leave this empty) Grant Type: Authorization Code
You can find details at here