Look for a pattern in the distances you have measured. A certain fixed amount of light is coming through the hole in the first card. Remember how the light got dimmer and harder to measure as you moved away. Suppose an ant were on your grid card looking at the light. Apply the ideas from your analysis to how bright the sun would look to a person on each of the planets.
Astronomers measure the distance from the sun to each planet in astronomical units.
One astronomical unit is the distance from the sun to the Earth. Remove the card with the hole from your meter stick. Fold the card and cut out tiny wedges to make different shaped holes. Remember to be careful with sharp objects. The holes should no more than 5 millimeters.