Use basic units Mass, Length, or Time so you can get all other units you need.
Force=Mass⋅Acceleration=Mass⋅LengthTime2
Pressure=ForceArea=MassLength⋅Time2
Energy=Force⋅Length=Mass⋅Length2Time2
Density=MassVolume=MassLength3
Acceleration=LengthTime2
Volume=Length3
For example, using base unit [kg], [mm], or [ms], will provide the following units force, pressure or
density.
Force=Mass⋅LengthTime2=[kg]⋅[mm][ms]2=103[kg]⋅[m][s]2=[kN]
Pressure=MassLength⋅Time2=[kg][mm]⋅[ms]2=109[kg][m]⋅[s]2=[GPa]
Energy=Mass⋅Length2Time2=[kg]⋅[mm]2[ms]2=[kg]⋅[m]2[s]2=[J]
Density=MassLength3=[kg][mm]2=106⋅[kg][m]2