We are sorry to say this is not not part of our of the box reporting. If you would like this to be added, please make a feature request here.
In the meantime, you have two options:
1. Click the link below to use our tool to export opportunity system changes:
You will have to select system and opportunities:
The final result will look something like this. You can roll up the stage changes and do your own reporting:
2. What you can also do is download our add-on "Report Builder" to download your data into a Google sheet and build your own lead conversion report. Your People and Opportunity export will have a "lead created date" column which you can roll up into your own reporting: Click to download the add on
Tips on custom report building: link
If you have any questions on how this works, please join one of our daily open office hours: