I am new to Power Query and am trying to combine 30 raw data files into two groups separately. Each group has its column headers and data.

When importing the files into Transform Data page, I need to create a new column as a filter so that I can split the two groups for combining. The new column can ideally display a specific cell value from each raw data file, such as cell value from B2 or B3 etc.

Screenshot

After searching the internet, I guessed some simple column formula for Custom Column with no luck:

=Excel.CurrentWorkbook(){2}[column3]

=Csv.Document(File.Contents([Folder Path]&[Name])){1}[Column1]

Wonder how can I make them work, or if there is other way I can use for filtering the raw data files. Many thanks.