Welcome to the community forums @Rayan_Alsubhi!
The new MONGODB-AWS authentication mechanism currently requires an Atlas cluster running MongoDB 4.4+.
Borrowing from the MongoDB 4.4 connection string documentation:
To use
MONGODB-AWS, you must be connecting to a MongoDB Atlas cluster which has been configured to support authentication via AWS IAM credentials (i.e. an AWS access key ID and a secret access key, and optionally an AWS session token). TheMONGODB-AWSauthentication mechanism requires that theauthSourcebe set to$external.
Regards,
Stennie