Gallons (volume) and feet (length) are not compatible units. I guess you mean cubic feet.
Apparently, 1 gal = 231 in³, so
32 gal/min
= (32 gal/min) • (231 in³/gal) • (1/12 ft/in)³ • (1/60 min/s)
= (32 • 231) / (12³ • 60) ft³/s
= 77/1080 ft³/s
≈ 0.0713 ft³/s
