Hi @shsalami ,
The error you're encountering suggests you are attempting to read a Delta table as if it were a collection of CSV files using the cloud_files function.
You may run "DESCRIBE DETAIL customers" and check whether this table exists and it is located in "/databricks-datasets/retail-org/customers/". The other way is to navigate to this location in your cloud storage. It may happen that you already created a Delta table in that location before. The syntax for reading from delta table is different.