Where does an FMS wind information comes from to calculate V approach?
It uses the wind entered in the PERF APPR page to correct the computed VAPP:

Takeoff, performance and go around speeds
[...]
The FMGC uses the performance model and either the predicted landing weight or the
current gross weight at transition to the approach phase to compute approach speeds
(VLS, VAPP, F, S, Green Dot). On the PERF APPR page, the selected LDG CONF determines
the applicable VLS and VAPP, the latter being updated by the WIND correction that the pilot
enters on the same page.

(A320 FCOM - Autoflight - Flight Management - Performance, emphasis mine)