Register car(s) with 50% G

Moin Moin! In the title line it already says. Several cars are running on my name and I have not used the tax advantages of the mark G so far. Tomorrow (or the days) I wanted to go to the registration office and register them at the new place of residence. What do I have to consider in order to get the discount? Do I have to go somewhere else than to the registration office? Do I need documents besides the SBA? And how much do I have to pay instead of €287? 143 €? 144 €? 143.50 €? I could’ve asked you a lot earlier… I hope you’ll still help me, dear Meehster.