Question

Where in a data table should units of measurement be shown?
in a separate column after the column of data values
in parentheses, in the title of the table
in the headings of columns that list the data values
in a note next to an asterisk, below the table

Answer 1

in the headings of columns that list the data values

This makes the units clear for each column without repeating them in every cell. (If the same unit applies to every column, you can also state it in the table title or a note, but column headings are the standard practice.)