How to measure or dimension an arc between two points.
To measure the distance between 2 points on an arc, you can use the "Measure Distance" from the Measure tool box.
By selecting snap points between the arc, like end points/intersections/midpoints, etc with the option method changes to "Along Element" ,
"Measure Length” from the Measure tool box, identify and select the arc to be measured,
In the “Dimension Styles” setting box, you need to first change the Angle Format: Unit to "Length” under the category tab of "Unit Format".
Then from the Dimension toolbox, select “Arc Size" from the Dimension Angular tool.