Answer: 2300.
Explanation:
There are 1000 millimeters in a meter.
There are 100 centimeters in a meter.
There are 10 millimeters in a meter.
Multiply the number of meters by 1000 giving us 2000.
Multiply the number of centimeters by 100 giving us 300.
Add the numbers together to get 2300.
Bonus info
Milli: 1000
Centi: 100
That information should probably help you with other measurement conversions when you take chemistry or physics.
Have a nice day! :) Good luck with the rest of middle school.