For one sided closed pipe$:$
Frequency, $\nu_{n}=\frac{(2 n-1) v}{4 L} \quad$ where $n=1,2,3 \ldots \ldots$
When length of the pipe is $25 \mathrm{cm}$ OR $0.25 \mathrm{m}, \quad 1750=\frac{(2 n-1) 350}{4 \times 0.25}$
$\Longrightarrow n=3$
Now let the length of the pipe after raising be $L m$
For minimum increase in length of air column, $n=3+1=4$
$\Longrightarrow 1750=\frac{(2 \times 4-1) 350}{4 \times L}$ gives $L=0.35 \mathrm{m}$
Thus the distance by which the pipe is raised $=0.35-0.25=0.1 m=10 c m$