Start with DP-203
Note that this is meant to validate your data engineering skills - so I'd not necessarily qualify this as being an Azure Databricks expert - but this is a meaningful start. Beyond that, you'd want to explore MS Learn (https://learn.microsoft.com/en-us/azure/databricks/ ) which is actually quite comprehensive (especially if you want to focus on the Azure part)
If the above response helps answer your question, remember to "Accept Answer" so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.
hth
Marcin