you need to configure source snapshot policy and assign it to volumes within source SVM to create snapshots with snapmirror label 6-hourly
Snapmirror mirror-vault type doesn't create any snapshots on the source apart of the sm-created snapshot at the moment of the snapmirror update. It looks for the snapshots with desired snapmirror-label
Please take a look here
https://docs.netapp.com/us-en/ontap/data-protection/vault-archive-snapmirror-technology-concept.html