Log on the AWS console, go to Users > Security credentials create an access key ID and Secret Access Key, find the region name here: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.RegionsAndAvailabilityZones.html
aws configure to configure the account setup.
then you can use
aws s3 ls to list all the bucket. or use command
aws s3 ls bucket_name/folder_structure/ to list the content in the folder.
Note that the / in the end maters, without which you only list the folder properties, not the content.