Stock Forecasting: How do I transform these ERP tables into this visual?

Hello, 

I have several tables from an ERP database that I am trying to transform in order to create a stock forecasting model. 

Here are the tables I am starting with (there is also a date table):

I then merge the products table with the invoices table in order to add calculated columns for the servings sold by invoice line:

Here is what I am trying to make: The visual on the right is a matrix that shows data related to our products, and the visual on the left contains product groups that filters the visual on the right. 

I'm just not sure what transformations I need to do in order to make this kind of visual. Through merging and pivoting, I can create a table that looks like the one I am trying to create, but the creation of that table loses the product_id relationship so it can't be filtered. The merged invoice lines table has all of the data I want, and is filterable, but all of the fields are values. When I put it into a matrix visual, I don't know how to get the left column to contain the row description.  

Essentially, I can easily create a measure that calculated units sold, but that measure only provides the values I want in the matrix. How do I get the name of the measure into the left column of the matrix visual, while maintaining the product_id relationship?

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Edit:
To be more specific/concise, I want to put measures into the rows of a matrix and have the columns be months.