Beginner help pls!

So I have a problem that I believe to be relatively simple I just can't seem to figure it out. It's probably in the way I organize the data begin to begin with.

I have a years worth of performance data, and various employees, organized by month. How do I combine my 12 Excel sheets And presented in A logical way?

Manually is taking forever I asked to be enrolled with power bi because I was more statistics person but doesn't seem to be moving along... l'd like to compare employees and their individual changes, but I don't know where to start.

Is there some sort of program that can combine this info, there's various name, changes, and other things, over time so doing it manually is insanely monotonous

Very open to a tutorial series if you can think of one. Eventually training in SQL but for now stuck with my multiple excel sheets lol.