Page 21 of your owners manual
These numbers identify the motorcycle model and should always be indicated when ordering spare parts.
The engine identification number is located in the motorcycle front side on the horizontal head cylinder lower side, near the starter motor and the generator cover."
Don't have an owners manual?
A digital copy for all owners manuals can be found on Ducati's website under maintenance. I suggest downloading it and reading it cover to cover. Put it on your phone so it's always with you.
And lastly, this question would have been more appropriate under your model specific sub topic.
Hope this helps,