Assuming $ T_1$ is non empty. Prove $ T_1$ is finite if there exists bijection from $ T_1$ to another finite set $ T_2$

Now we have $ h : J_m \to T_1$

Assume another finite set $ T_2$ , so we have $ h_1 : J_m \to T_2$ .

Since both $ h_1$ and $ h_2$ are bijections. so is $ h_1 \circ h^{-1}$

$ J_m$ = $ {1,2,3,…,m$ }

Conversely, similar idea to that of this. But is this even correct ?

Thanks