In order to facilitate the redesign that has come with the new Fundamentals release some object names have been changed. These are:

• Milestones Project which has had the label changed to Project 
• Milestones Phase which has had the label changed to Phase
• Milestones Task which has had the label changed to Project Task
• Milestones Sub Task which has had the label changed to Sub Tasks
• Milestones Assignments – the API name has been changed to Milestones_Assignment2

This should not affect how your users interact with the system on a daily basis. However, any automation such as Process Builders, Flows, Approval Processes and Email Alerts will need to be updated.

To ensure that your functionality remains consistent during the switch from Milestones to Fundamentals you should

1. Install Fundamentals in a Sandbox first, this will allow you to see where functionality is affected
2. Make a detailed list of any automation triggered by, or containing, the objects listed above, these are the pieces that will need to be updated
3. Recreate each piece of automation keeping everything the same except for the object name that will need to be substituted 
4. Test in the Sandbox that functionality is consistent with your production org
5. Use your preferred method to transfer the build out when you upgrade your production org
6. Do a final functionality test to check nothing has been missed
7. Delete the old automation

Read more about the name change here!