How to format output to csv from "Get-AzureADAuditDirectoryLogs" ?

 

I'm working with command "Get-AzureADAuditDirectoryLogs" to store Azure Log locally. The result look like json but I failed to use "convertfrom-json" to get those data separately to column. Does anyone know which is this kind of output and how I can convert it to csv ? All I need is get output in "UserPrincipalName".