With
ISO, I'd go higher(as I've said before) due to the camera you're using.
If you had a D800, I'd say keep it lower(eg. ISO3200, maybe 6400 max!)
With the D3500, I'd go ISO12800 max, for two reasons.
1. better
ISO quality at that level. Newer sensor design(same as the D5500). and the higher the
ISO, the higher the
shutter can be
2. you're camera is cropped by comparison to the D800, so with say a full frame(eg. D800) and a 300mm
lens, you're already cropped, whereas with a full frame you need to crop more. Cropping makes
ISO look worse than it really is.
But those maximums assume no cropping. If you subsequently need to crop then those higher
ISO values would be lowered a little, say ISO6400 on the D3500.