You can find any tool by the Menu Structure HERE: https://turbocaddoc.atlassian.net/wiki/display/TC21UG/Menu+Structure
You can find the menu location of any tool by name HERE: https://turbocaddoc.atlassian.net/wiki/display/TC21UG/Tools+Mapped+to+Menus
Curve Length
This tool works exactly the same as the Measure Distance.
Click on a 2D or 3D curve. Its length is displayed in the Measurement Info Palette.
Select a second point on the curve to measure a partial length of the curve.