Update Source in Same Access Database to Different Table in Database

I searched before to see if this was answered and didn't find anything. Sorry if it has; I may have just have the wrong search values.

I have an Access database with a table per each month. As I get new data at the end of each month the data is transformed and saved in the Access database.

I then create a Excel file and use Power Query to connect to the database. I'll create a Pivot Table output based on that connected data. In that Excel file I will make calculations and other manipulations of the connected data in the Pivot Table. When a new month comes, new table in the same original database saved in the same location (example: 01 Jan, 02 Feb...). I create a copy of the Excel file with the calculations (save off the last one from last month). New data has YTD data so I still have all of last month's data on top of new data.

My questions are:

1) How do I change the original Excel file with all my calcualtions connection from table 1 to table 2 with the new data?

I essentially want to make a connected Excel file with specific calculations that I can change what table of data in the database every month/12 different times a year. 

I attempted to change the source but I broke the connection.