An AWS account is an ownership and access boundary. A Region is a geographic area containing separate Availability Zones. Many resources, including EC2 instances, belong to a Region; an empty resource table in one Region doesn't prove that the account is empty. IAM is a global service, while an ARN describes a particular resource using a service-specific structure.
This course uses a local training account. You don't need cloud credentials, and these commands don't create real resources or charges. Start by checking the account and Region displayed above the console. Then inspect the service and resource type. A bucket name and an EC2 instance identifier aren't interchangeable, even when both belong to the same account.