Hello itay4,
To get the list of all incidents try and run this request: https://api.security.microsoft.com/api/incidents. This should give you all the incidents in your tenant and the associated alerts.
To get the specific incident try running this request: https://api.security.microsoft.com/api/incidents/{incidentId}?tid={tenantId}. Replace the incidentId with the relevant Id and the tenantId with your tenantId.
I hope this helps answer your question.