Unfortunately, there is no API available for this.
The “/networks/{networkId}/clients/{clientId}/usageHistory” endpoint you are using provides usage history per client, which does not directly correlate with the port traffic data shown in the dashboard.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.