I'm sure someone smarter than me can come up with a better way but you could run a SQL query and anything that has an owner would be a custom report and any report that the owner field equals NULL is out of the box.
SELECT [Name],[Owner],[Type] FROM [dbo].[ReportDefinitions] WHERE [Owner] <> 'Custom'
Hi neomatrix1217 thanks for reply
Yes we can able to segregate canned report the way u suggested
But I have different issue , recently we have build new environment of Orion and we have brought more than 100 reports from old server
now we does not have the owners of those Old reports in New server and it shows owner as Null for custom reports :-)