As I can see in the screenshots, you are entering incorrect connection string. Various parameters are not separated by blank spaces.
Please follow the steps mentioned below. Open your Atlas Cluster.
Click on Connect
After that click on Connect with the Mongo Shell
Then select I have the Mongo Shell installed. Select the 3.6 or later version. Finally click on the Copy button and then go ahead and paste the connection string in your windows terminal.
The terminal will ask for the Password, go ahead and enter the password. After following the above mentioned steps you should be able to connect to your cluster.
If the issue still persists, feel free to get back to us. Happy Learning
Curriculum Support Engineer