convert the rate into the given units.
there are 128 oz in 1 gal, and 3600 sec in 1 hour. So, the conversion factors are:
6 oz/sec * [1 gal / 128 oz] * [3600 sec / hour]
which gives you
6 * 3600/ 128 = 168.5 gal/hour
note that oz in this case refer to fluid ounces. If you’re referring to the actual weight, you need to know the density of the fluid.