We're already in trouble, even before we start working on this question.
"Gram" is a unit of mass, not a unit of weight or force. So no matter how we manipulate it or massage it, there's no way to convert it to "lbs". The best we can do is take 'g' to mean 'the WEIGHT of a gram of mass', and then decide which planet we want to solve the question for, since 1 gram has a different weight on every different planet.
I've decided to solve it for Earth, where 1 gram of mass weighs 0.035 oz or 0.0022 lb.
(636 gram-weight-on-Earth/cm) (0.0022 lb/gram-weight) (1 cm / 0.0328 foot) =
(636 · 0.0022 / 0.0328) (gm-lb-cm / cm-gm-foot) =
42.74 lb/foot
