Your goal here is to convert the number of moles of sodium fluoride to grams.
To do that, you can use the molar mass of the compound, which tells you the mass of exactly
Sodium fluoride has a molar mass of
You can thus say that your sample will have a mass of
#4.5 color(red)(cancel(color(black)("moles NaF"))) * overbrace("41.998 g"/(1color(red)(cancel(color(black)("mole NaF")))))^(color(blue)("the molar mass of NaF")) = color(darkgreen)(ul(color(black)("190 g")))#
The answer is rounded to two sig figs, the number of sig figs you have for the number of moles present in your sample.