Outlook 2016 for Mac stores its database in:
Users/*Name*/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/
When the application does a database rebuild it is going to create a backup copy and place it into the above folder. Therefore please ensure there is sufficient storage space before you start to rebuild the database.
NOTE: The site owner shares his work-related information. Some information/solutions are available on the internet.
