For client_credentials you don't need any scopes. You'd need to enable Kinde Management API for the backend / regular web app, as it is not enabled by default.
Using Client Credentials to get an Access Token
Machine to machine application.
Kinde Management API for it with the toggle switch and hit save

In Postman, head to the Collections tab on the left, and create a new one called “Kinde”.
In the 3 dots menu next to your new Kinde folder, select Add request.

A new GET request should appear under the folder. Change it to a POST request and renamed to client_credentials.
Set up the Authorization menu item to look like the below. The orange text e.g {{business_domain}} is replaced with the variables you set above automatically when you make a request

Set the audience under Advanced Options to be as follows:

Make sure the Headers menu item contains the below:
