Moles are amount of substance.
Baking soda formula is - NaHCO₃
molar masses of individual atoms are
Na - 23 g/mol
H - 1 g/mol
C - 12 g/mol
O - 16 g/mol
molar mass of NaHCO₃ - 23 + 1 + 12 + (16x 3) = 84 g/mol
mass of 1 mol of NaHCO₃ is - 84 g
then mass of 6.983 mol is - 84 g/mol x 6.983 mol = 587 g
In kg the mass in g should be divided by 1000
mass of baking soda is = 0.587 kg