To see all autobackup files please use item/list_backups:

svc=item/list_backups&params={"itemId":<long>}

{
	"result": [
		{
			"date":<text>,		/* date */
			"t":<uint>,		/* creation time */
			"unitId":<long>,	/* item/unit id */
			"id":<long>,		/* file id */
			"name":			/* file name */
		}
	]
}