A phone charger sends a steady 1.2 A for 40 minutes…

A current is $I = Q/t$, and $N = Q/e$ electrons cross a section, with $e = 1.6 \times 10^{-19}$ C. The drift velocity is $v_d = eE\tau/m$ and the mobility is $\mu = v_d/E = e\tau/m$. The current is $I = nAev_d$, so $v_d = I/(nAe)$. The current density is $J = I/A = nev_d$.