Getting value from options dropdown

I need to pull the selected option in a dropdown menu and set it as the value of a text box. The text box is part of a form that users fill to enquire about a product. How do I go about doing this?

I am using the Webflow Ecommerce product collection as the source of the page, and the drop down comes from the production options. There is a hidden field called “Edition-Box” that’s supposed to automatically update with the selection.

Live page:
Here is my public share link: