Hello Alyssa,
There is no report can fulfill your requirement directly. You can try to create a custom report in work center Business Analytics. Or, there is a indirect way you may try.
1. Export the customer list into a excel.
2. Run sales order volume report to show in a time period which customer created sales order.
3. Export the report into excel. Compare these 2 lists, you will get the inactive customers.
Hope it can anyhow bring an idea to you.
Thanks,
Adie