Rough figure

Whenever there's an atleast in the wording of the question, we can use case cancellation method.

Total number of ways of filling 6 Ps in 8 squares is equal to $\Large \frac{8!}{2! 6!}$ = 28.

Now notice that if we have to fill 6 Ps in only two columns, there are 2 ways to do that ( the middle column+one of the two side columns are taken).

To fill them in one column would be an impossible case.

Now cancelling 2 from 28, we get 26 as the answer.

There are 8C6 ways to put the P's. The only "2 cases" when there will be no P in at least one column is either the rightmost column being empty or the leftmost column being emty. Hence the answer is 8C6-2=26.