The problem above is simply a conversion problem. We only need a conversion factor to convert the units from amu to kg. From a conversion table, we will see that 1 amu is equal to 1.66x10^-27 kg. We convert as follows:
0.13261 amu ( 1.66 × 10^-27 kg / 1 amu ) = 2.20x10^-28 kg