Both Nikon D3500 and Pentax KF have 24.0 MP resolution sensors but Nikon D3500's sensor is APS-C (23.5 x 15.6 mm ) and Pentax KF's sensor is APS-C (23.5 x 15.6 mm ).
Since Pentax KF's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Nikon D3500.
Another similarity between these two cameras is that both Pentax KF and Nikon D3500 sensors lack anti-alias (Low-Pass) filters. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the D3500 and KF sensor size comparison.
Nikon D3500 and Pentax KF have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.