Below you can see the front view size comparison of Nikon D3500 and Fujifilm X-T10. Fujifilm X-T10 is clearly the smaller of the two cameras. Its body is 6mm narrower, 14mm shorter and 29mm thinner than Nikon D3500.
Nikon D3500 vs Fujifilm X-T10 - Front View
Nikon D3500 vs Fujifilm X-T10 - Top View
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.
Camera Size Comparison
Select Two Cameras for Size Comparison