Answer
$516.59\text{ mg}$
Work Step by Step
Convert ounces to grams:
$1\text{ ounce}=28.3495\text{ g}$
$8.2\text{ oz}\times 28.3495=232.466\text{ g}$
Calculate fluoride content:
Toothpaste contains 1.00 mg of fluoride per gram:
$232.466\text{ g}\times 1.00\text{ mg/g}=232.466\text{ mg}$
Calculate $NaF$ needed to supply that fluoride:
$\text{ NaF mass}=\frac{232.466\text{ mg}}{0.45}\approx 516.59\text{ mg}$
