First we need to define some things:
m means meters
mm means millimeters
cm means centimeters
1 m = 100 cm
1 mm = 0.1 cm
They are asking for us to convert 23.6 cm to m and mm
Lets start with 23.6 cm to m:

(the cm's cancel each other out)
Convert 23.6 cm to mm:

(again the cm's cancel out)
Hope this helps!