How can I add more seats to any police car

Hi, I was looking for some new things and I saw No-Pixel new victoria that has 3 seats on back. I searched it on everywhere but I couldn’t find anything to learn “how to add more seats to cars” or “to police cars”. I tried to look at the meta files but I couldn’t do anything. Can someone help me about this?

Several people here have already tried to find an answer to this question!

I saw those topics but its been over 1 year. Thats why I opened new topic and I’m looking for something like tutorial or someone that can tell me about example.