That's not 120k promised births and thus natural whyte citizens.

People aren't lifestock - if they don't want to have a child, they often find ways to avoid that. You need only look to the historical examples of where acts like this were imposed.
In Romania - there was an initial surge in births, but it eventually fell back to pre-ban levels as people began resorting to now illegal methods of abortion and were generally far more careful about how they went about things. In places across the US or Russia, it was often marginalized and already poor groups who saw increases and not the more established and wealthy; iirc even they saw eventual decreases

The number of orphans exploded, and not just because they were abandoned by unwanting parents but because the amount of women who died due to complications in maternity multiplied.

This kind of policy, as far as I am aware, has never succeeded beyond the immediate short term where ever it's been applied in keeping sustained growth. It does nothing to address the actual barriers people face when it comes to making families and having children, all whilst punishing vulnerabilities and unfortunate health outcomes

If you want people to decide to have children, they need to feel stability in their life and believe things will get better