Tracking days in stage for pipeline in custom module

Tracking days in stage for pipeline in custom module

Hello,

We have a custom module in which we track the different onboarding stages for our SaaS platform.

Ie:
New
Onboarding Planned
Account Prepared
Onboarded
Login sent
Service Call


I would like to create a dashboard report that shows me the average time a customer was in a certain stage before moving to the next in the previous month.

How would I create this report?