How Important is Transmission Fluid?

So I was playing around my new car in checking all the fluids when I noticed I can’t find the transmission fluid. How do I know my car has transmission fluid. how do I change the transmission fluid? What happens when I do not have transmission fluid inside of my transmission? I’m kinda worried that my vehicle doesn’t have any of this fluid in it because I cannot find it.

What color is transmission fluid and where is the sound? I’ve tried searching in my engine bay for a dipstick orapred device. I just can’t seem to find this transmission fluid though. I understand the fact of the fluid being in the transmission but I don’t know where the transmission is. I am the owner of a pickup truck and I think it is rear wheel drive.

The previous owner of the vehicle said he has never changed the transmission fluid. that’s what makes me very interested in changing the fluid myself. After 200,000 miles I’m sure the transmission fluid good really use a change.