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Standard rule for 18 DIN bindings is that if you have to ask if you need an 18 DIN binding, you don't need an 18 DIN binding.
That said, depending on BSL and skier level and a few other things a rider around that size would be probably skiing 8-10 DIN which is perfectly fine on those bindings (well, 9-10 on the STH)
Disclaimer: If you use DIN or binding information given to you by someone on an internet forum your legs will turn into pieces of bamboo and be chopped up by ski patrol to use as trail markers. So don't do it.