You can create a Unit and then specify the Quantity Kind that it uses.
Note that the SysML profile includes standard SI Definition Units that you can use, such as Hertz, Newton and Watt - the SI Definition Units are provided in sub-Packages of the SI Definitions package.
To create a unit:
1. Right-click the Model or Package in which you want to create the unit, point to New, point to SysML, point to Structure, and then click Unit.
2. Type the required name of the Unit, and then press the Enter key.
Alternatively, you can create a Unit on a Block Definition Diagram.
How?
To specify a unit's quantity kind:
1. Right-click the Unit, point to Links, and then click Quantity Kind.
2. To use an existing Quantity Kind:
a. Select the Existing Item option.
b. Select the Quantity Kind that you want to use, and then click OK.
To create a new Quantity Kind to use:
a. Select the New Item option.
b. In the Name box type the name of the Quantity Kind that will be created, and then click OK.
To unset a unit's quantity kind:
1. Right-click the Unit, point to Links, and then click Quantity Kind.
SI Definitions package.