Depending on brand, size, shape and over  inflation this may differ.

Using the amount of cubic feet from step 1 you can work out which size bottle and how many:

Heli Box 30 = 9 Cubic Feet per tank
Heli Box 50 = 15 Cubic Feet per tank

V Size = 63 Cubic Feet per tank
T Size = 127 Cubic Feet per tank
L Size = 317 Cubic Feet per tank
E33 Size = 302 Cubic Feet per tank
GENIE 10 Size = 91 Cubic Feet per tank
GENIE 20 Size = 183 Cubic Feet per tank