Navigate to Customers / Advanced Search / Order History Search /
Use the following two Search Criteria:
Customers who have placed at most “1” Orders;
Customers who have not ordered since “__(whatever date makes sense here for your requirement)__” /
(So, for example, if you want to find folks who have ordered at some point, but not within the past three months, then you would pick the date that is three months ago today, for the second criteria.)
Then click Search.