m^-1 同 m^-2

Your question is not specific enough.

But I think you wish to ask the difference between [per metre] and [per metre square]

These are suffices of units used in physics, usually they are expressed together with another physical quantities. Examples are:

Electric field intensity, unit in volts per metre (v.m^-1)

Pressure, unit in newtons per metre square (N.m^-2)

. m^-1
= 1/m^1

. m^-2
= 1/m^2