Both Nikon D3500 and Sony A6000 have 24.0 MP resolution sensors but Nikon D3500's sensor is APS-C (23.5 x 15.6 mm ) and Sony A6000's sensor is APS-C (23.5 x 15.6 mm ).
Since Sony A6000'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 difference between these two cameras is that Nikon D3500's sensor lacks anti-alias (Low-Pass) filter. 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 A6000 sensor size comparison.
Nikon D3500 and Sony A6000 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.