How can I create a list of specific values ("Nas*" values) from a csv file when the values are in many separate columns?

I want to create a list of specific values (values that begin with “Nas*”) from my csv file, but the values of “Nas*” are in 100 different columns in my csv file.

Because they’re not all in one column, I cannot generate this list. Only lists of one column at a time but that is not feasible due to the large number of columns.