You're asking about the scale of Venus, but you've only provided the diameter of the Sun. To figure out the scale of Venus, we need more information! Here's why:

What is "scale" in this context?

* Scale Model: If you're asking for the size of a model of Venus that would be in proportion to a 3000 mm diameter Sun model, we need to know the actual diameter of Venus.

* Relative Size: If you want to know how much smaller Venus is than the Sun, we still need the actual diameter of Venus.

Here's what we need to know:

1. The actual diameter of Venus: This is approximately 12,104 km.

2. What kind of scale you want: A ratio of 1:100,000 would mean 1 mm on your model represents 100,000 mm in reality.

Example:

Let's say you want a scale model where 1 mm represents 100,000 km in reality.

* Sun model: 3000 mm (given)

* Venus actual diameter: 12,104 km = 12,104,000,000 mm

* Venus model size: 12,104,000,000 mm / 100,000 = 121.04 mm

Therefore, in this example, your Venus model would be 121.04 mm in diameter.

Let me know what kind of scale you're looking for, and I can help you calculate the size of your Venus model!