
Actually Welcome to the Concept of the SURFACE AREAS AND VOLUMES.
Since the given section is a Sector of a Circle with length as, 8πcm .
Thus then it's folded veltically at an axis to make a cone.
since we know that, The Curved surface area of a cone is given as formula,
C.S.A = πrl
where, r = radius and l = slant height.
also 2πr = circumference of a circle,
we get as, radius = 4 cm.