\[\large 100cm=1m \qquad \rightarrow \qquad \frac{100cm}{1m}=1\]We can multiply by \(1\) because it won't change the `value` of our expression, it will just change the units.\[\large \frac{15N}{cm}(1) \qquad \rightarrow \qquad \frac{15N}{cm}\left(\frac{100cm}{m}\right)\]The centimeters will cancel out,\[\large \frac{15N}{\cancel{cm}}\left(\frac{100\cancel{cm}}{m}\right)\]Leaving us with,\[\large \frac{1500N}{m}\]