Whip out your trusty E6B/CR-3/CR-2, set the planned ground speed at the speed index and read the required FPM above the required feet per nm.
Theory: If you are doing the set GS, you'll have the GS in nm per minute above 10 on the inner scale. Multiply nm per minute by feet per nm, i e read above the feet per nm rather than above 10, and you get the fpm.
Cheers,
Fred