how do I calculate 25,000 shares of 1% cumulative preferred stock of $100 par

The 1% is referring to 1% of the par value. That will be the annual required dividend per share, and you have a total of 25,000 shares.

All that is going to do, though, is give you the required annual amount. That doesn't mean that it will actually end up being paid, so you can only know what it's supposed to be with that information, and not necessarily what it actually was in any one year.