Update field by the field of other object

So i'm building the CRM

I have Sales order date field in Sales order object.

I have Last sales order date field in Customer object. This field will show the latest date that customer buy from us.

My customer and sales order are linked and I can pull the sales order date data from sales order that are linked with each customer to show in the page.

My ideal is to get those date and select only the latest date and copy it into my Last sales order date field in Customer object.