After Effects does not render on the GPU. So you can't do what you are asking.
That being said, in the latest version, three effects (Lumetri, the new Gaussian blur, and Sharpen) can be accelerated by the GPU.
There is an obsolete way to create 3d geometry in After Effects called the ray-traced renderer. That can use the GPU to accelerate it too, but it's the old way to do things, so I wouldn't mess with it.
Some third-party plugins (like Element 3d, Red Giant Universe, ShapeShifter, etc.) render on the GPU so you should see some activity if you use something like them.