A thermometer.
Celsius.
The answer will depend on what aspect of the calculator you wish to measure: its length, volume, mass, weight, temperature, etc.
I would use centimetres.
Centimeters
Unit for time is a second.There are various instruments to measure temperature: a thermometer, a thermocouple are two.
A microgram.
Potatoes are sold by the kilogram.
To measure the mm of an item you would need to use a metric ruler. The metric ruler has cm and mm on it.
If you mean measure height then it would be the metre if you mean measure weight it would be Kilograms
I would use centimeteres.
meters
Square metres.