“ETL Code Sequence for Merging Old Product Order Data into a New Data Mart”

This finals assignment is from a first year SQL class I have been struggling with for different reasons and have been using AI to help with understanding. Unfortunately, this assignment is not as easy for me and my pal Gemini to follow together.
Here is the description of the assignment straight from the first page.
“Your company wants to merge its old product order data into a new data mart to facilitate analysis. You have been tasked with writing an ETL (extract, transform, and load) code sequence, and executing it on three years’ worth of order data. 
In this assignment, you will produce SQL code which scrubs and imports each of the three years’ worth of data, and produces an output file called stagingTable. 
Along with these instructions, there is another document, ‘Additional Clarification on the Week 6 Candy Assignment’. Please read that document carefully. 
You should also read the ‘Data Notes’ in part 3 of this document. It is very important that you understand the data and how the data changes over the three years, so you can create a ‘stagingTable’ the effectively combines the data that might have been captured in different ways over the years.
Let’s get started!