There could be multiple reasone why you're getting this error @avishkarborkar . If the course you're following requires Unity Catalog, first you need to check if you have a premium workspace. Next you need to make sure that your workspace is enabled for Unity Catalog (you need to assign it to a regional metastore in account console).
Enable a workspace for Unity Catalog - Azure Databricks | Microsoft Learn
Then, you need to have a proper cluster which supports Unity Catalog.

For further troubleshooting ideas you can refer to below article:

Workspace is not UC enabled - Databricks