The Import sets and Rows of it will be deleted and will retain only the last 7days of data. This is due to the job "Import Set Deleter". This document talks about the possible ways to retrieve the deleted data which is of more than 7days.

Unfortunately, there no possible ways to retrieve the data of a table or records once it's rotated within the instance.

But we store the Last 28days of backup from the database. So the only option is to restore the backup of the data that has been deleted based on the backup date.

If it's on Sub-Prod instances, you can restore the backup on the same instance.

In case of a Production instance, you can restore the backup on to your test or dev instance to get the data.

Or you can log a case with Support to request a temp instance and restore the backup of the requested date.

Please follow up the below KB to restore the backup:

Restoring an instance with the Now Support (HI) Service Catalog

Note: The Catalog Item will only be available to your Hi Portal Admin account for your company to request the restoration of the backup.