The problem asks to convert $0.65$ dag (decagrams) to mg (milligrams).

1. Problem Description

The problem asks to convert $0.65$ dag (decagrams) to mg (milligrams).

2. Solution Steps

We need to convert decagrams (dag) to milligrams (mg).

First, we convert decagrams to grams (g):

$1 \text{ dag} = 10 \text{ g}$

Then, we convert grams to milligrams (mg):

$1 \text{ g} = 1000 \text{ mg}$

Therefore, we can write the conversion factor from dag to mg as:

$1 \text{ dag} = 10 \text{ g} = 10 \times 1000 \text{ mg} = 10000 \text{ mg}$

Now, we convert $0.65$ dag to mg:

$0.65 \text{ dag} = 0.65 \times 10000 \text{ mg} = 6500 \text{ mg}$

3. Final Answer

The final answer is 6500 mg.