Answer
$4.009\times10^{26}\ formula\ units$
Work Step by Step
Convert the mass of the sample to grams by multiplying by 1000 and then to moles by dividing by the molar mass of the compound. The multiply by Avagadro's number to get the number of molecules (or formula units for ionic compounds as they do not exist as individual molecules.
$55.93kg\ NaHCO_{3}\times\frac{1000\ g}{1\ kg}\times\frac{1mol\ NaHCO_{3}}{84.007g\ NaHCO_{3}}\times\frac{6.022\times10^{23}\ molecules}{1\ mol}= 4.009\times10^{26}\ formula\ units$