Cylindrical conductor and magnetic field intensity

A linear cylindrical conductor of infinite length is internally concave,
i.e. the area of ​​between $0 leq r leq alpha$ is filled by a vacuum, while the area of ​​$alpha leq r leq 2a$ is normally filled with copper. In the area $alpha leq r leq 2alpha$ the pipeline transmits the current $I$ with a current density $vec{J}$, parallel to its axis, which
is given by the relation: $vec{J}=J_0frac{rho}{alpha}vec{z}$, where
$J_0$ is a constant, and $rho$ is the distance from the $z$-axis of the conductor. Find the
expression of the magnetic field intensity $H$ everywhere in space.

It’s the first time I come across such an exercise and I was not taught about magnetic field intensity $H$ or how it may be linked to J. The only thing I have learnt about $J$ is that $J=I/A$. Can anyone please guide me through this exercise? Thank you!