You may use any 3rd Party tool to do that. ONTAP scans aggregates and volumes at the block-level. Therefore, there is no way from ONTAP to generate a cold data report at the file-level.
From Storage side, you can view the 'snapshots' date/time for the given volume (where data resides), to identify data that has been 'cold' [data that is not accessed] for more than say example - 30,60,90,120 days. You can sort this (snapshot) via CLI or script. Data that is in the Snapshot or active-file-system, will not report which files (names) are cold, it is the BLOCKS that are 'cold'. You could then either delete those Snapshots which are deemed outside of your compliance requirement, or have FabricPool tiering in place to Tier (send) those BLOCKs to lesser expansive storage/archive/cloud.
Is there a way to report file-level cold data?
https://kb.netapp.com/onprem/ontap/os/Is_there_a_way_to_report_file-level_cold_data%3F
FabricPool best practices:
https://www.netapp.com/pdf.html?item=/media/17239-tr4598pdf.pdf
