In order to answer this question, we must primarily consider a convex lens with a moderately thick center and a narrow edge at the bottom and higher ends that converges light rays that are parallel to its central axis. The diopter serves as a unit of measurement for lens power.

A convex lens's power:
According to the illustration below, the convex lens power is the capacity of the lens to concentrate light rays that strike it.

It can mathematically be defined as $P=\frac{1}{f}$when the focal length f is used.
S.I. A diopter is a unit of power.
It is symbolizedmeters by the capital letter "P."
Convex lenses' powers are known to be inversely related to their focal lengths in metres.
and the focal length unit is the meter.
Consequently, the power meter's unit${}^{-1}\left({ \mathrm{m}}^{-1}\right)$.

Hence, the correct answer is option A.