The aws efs describe-file-systems command can be used to list the Elastic File Systems (EFS) that have been created.

aws efs describe-file-systems

And here is an example of how to limit the output using the --query option.

aws efs describe-file-systems --query 'FileSystems[?Name==`my-efs`]'

Something like this should be returned.

{
    "FileSystems": [
        {
            "OwnerId": "123456789012",
            "CreationToken": "my-efs",
            "FileSystemId": "fs-0d1500aa4f4b50839",
            "FileSystemArn": "arn:aws:elasticfilesystem:us-east-1:123456789012:file-system/fs-0d1500aa4f4b50839",
            "CreationTime": "2023-09-27T04:55:23+00:00",
            "LifeCycleState": "available",
            "Name": "my-efs",
            "NumberOfMountTargets": 1,
            "SizeInBytes": {
                "Value": 24576,
                "Timestamp": "2023-10-02T10:13:00+00:00",
                "ValueInIA": 0,
                "ValueInStandard": 24576
            },
            "PerformanceMode": "generalPurpose",
            "Encrypted": true,
            "KmsKeyId": "arn:aws:kms:us-east-1:123456789012:key/f0c9f7f5-1956-4b8d-bb2f-e0f9aa951309",
            "ThroughputMode": "bursting",
            "Tags": [
                {
                    "Key": "Name",
                    "Value": "my-efs"
                },
                {
                    "Key": "Role",
                    "Value": "AWS EFS File Storage"
                }
            ]
        }
    ]
}