Entering data correctly

Hello everyone!

I would love to consult with you about entering data into Power BI
In the tool I have a database connected to the WEB One drive Excel file containing the year 2021
I have built complete reports based on this data
Now I got another database which is also an excel file exactly the same as the previous one only contains the year 2020
I have an index column in both
I'm debating how to connect the files so I can see the year 2020 connects to the existing data