Answer:
You can do this by rolling dice 4 times
Explanation:
If you roll a fair dice 4 times and record the findings and their orders, you can generate 6^4= 1296 possible outcomes. You can pick 1-1000 as numbers and then re-roll all the dice if the number generate 1001-1296
To translate the dice result into a number you have to multiply the dice result as following:
1st roll multiplied by 6^0 = 1
2nd roll multiplied by 6^1 = 6
3rd roll multiplied by 6^2= 36
4th roll multiplied by 6^3= 216
Let's say you roll 1, 2, 3, 4
The number generated will be: 1*1 + 2 *6 + 3 *36 + 4 *216 = 985