If the u. s. were to totally convert to metrics, how would you go about doing that?

Achildren’s pain relief elixir contains 80. mg acetaminophen per 0.50 teaspoon. the dosage recommended for a child who weighs between 24 and 35 lb is 1.5 teaspoons. what is the range of acetaminophen doses, expressed in mg acetaminophen/kg body weight, for children who weigh between 24 and 35 lb