Import monthly data automatically

Hi, 

I have a Power BI model where I have monthly data from 12 suppliers. So, I get in total 12 new reports every month from suppliers in seperate excel files. The excel template for all suppliers are same with same number of  columns and column names. For example, "Supplier name", "Date", "Amount", "Cost". Then, I need to combine these 12 excel files into one excel file, make some changes like add a column to identify each transaction, and then import this one big file to the Power BI model. 1) I would like to know if I can somehow automate importing process so that each excel file coming seperately from suppliers every month automatically get imported to the Power BI model? 2)  If it is not possible, alternatively, is it possible to automatically add monthly reports to my one big excel file every month which is the source of the Power BI model? The second alternative is probably not efficient since the big excel file will have performance issues after several months as new data is added every month.

Thanks in advance!

Regards,

Asif