I cannot find the wheels engine and seats parts in the game the version is right and so is the mod but also when I spawn a car they fall through the floorand it says this

This is because you are missing the Parts pack required for Trin Civil Pack V3, which contains the wheels, seats, motors and other miscellaneous parts required for the vehicle to be assembled with.

https://www.curseforge.com/minecraft/mc-mods/trin-part-pack

In the future, remember to read through mod pages to ensure you aren't missing required dependencies such as this.

(P.S: With these vehicles you'll still have to put the wheels on. Some may have them by default, but with Trin V3 that is not the case yet.)