Check the picture below.
if the barrel is rolled up the ramp 26 times, each time the barrel is rolled up fully, it covers a length the circumference of its base, so if it does it 26 times, it wen up its base circumference 26 times.
[tex]\textit{circumference of a circle}\\\\ C=\pi d~~ \begin{cases} d=diameter\\[-0.5em] \hrulefill\\ d=2.5 \end{cases}\implies C=2.5\pi \implies \stackrel{\textit{26 times}}{C =65\pi }\implies \stackrel{\pi =3.14}{C=204.1}[/tex]
