Dear Student,
Dimension formula of force is: [F] = [MLT-2]
Hence: M = [FT2 /L]
GIVEN unit of force (F) = 100 N
Unit of length [L] = 10 m
Unit of time [T] = 100 sec
Putting all these values to M
M = 100*1002/10 = 100000 kg
Hence unit of mass will be 105 kg.