The magnetic field at the centre of a long solenoid is given by in terms of magnetic permeability in free space, 

$B={\mu }_{0}ni ...\left(1\right)$.

And magnetic intensity is given by

$H=\frac{B}{{\mu }_0}$

$\therefore H=ni$,              $$[using $\left(1\right)]$

$\Rightarrow 1000=n\times 2$

$\Rightarrow n=500 \mathrm{turns} {\mathrm{meter}}^{-1}$

$\Rightarrow n=5 \mathrm{turns} {\mathrm{cm}}^{-1}$