Read and manipulate multiple excel file

I have 4 excel files of same headers
i have 2 excel files of same headers

So i will merge them and output will be 2 excel files say Excel A and Excel B
Now there are 2 master files

And at last i have 1 Output file

The columns or the index place of the column headers arent matching

Example screenshot

Now i want to get all the data from those excel files and map it to output file
And if any cell get empty then mark it red

And then send mail saying this particular records column is empty

How do i do it

Hi @Goku ,
Your describe is not clear your requirement. I need clear more
I think can use LinQ,
Can you share your file
regards