  Assuming that the recently observed hidden-charm pentaquark state,
$P_c(4450)$, is of molecular nature as predicted in the unitary approach, we
propose to study the decay of $\Xi^-_b\rightarrow J/\psi K^- \Lambda$ to search
for the strangeness counterpart of the $P_c(4450)$. There are three ingredients
in the decay mechanism: the weak decay mechanism, the hadronization mechanism,
and the finite state interactions in the meson-baryon system of strangeness
$S=-2$ and isospin $I=1/2$ and of the $J/\psi\Lambda$. All these have been
tested extensively. As a result, we provide a genuine prediction of the
differential cross section where a strangeness hidden-charm pentaquark state,
the counterpart of the $P_c(4450)$, can be clearly seen. The decay rate is
estimated to be of similar magnitude as the $\Lambda_b^0\rightarrow J/\psi K^-
p$ observed by the LHCb collaboration.
