You should clarify what you want to measure about it: its diameter, mass, weight, color, etc. If you want to measure its diameter, that would usually be specified in microns (= micrometers).
feet
Metres
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.
You would use the metric unit "kilograms" to measure the weight of a bag of groceries.
You would use the metric unit "kilograms" to measure the weight of a sack of peaches.
A refrigerator would typically be measured in kilograms (kg) in terms of weight in the metric system.
The metric units used to measure the mass of your weight would be kilograms (kg) or grams (g).
The metric unit used to measure the weight of a snail is grams (g) or milligrams (mg).
You would most likely use milliters.
The weight of the box would be measured in grams.
A scale
Mass is measured in kilograms.
Every country in Europe uses the metric system, meaning they would measure weight in kilograms, grams, etc.
The metric unit for measuring human weight is actually the Newton (N). Newton's are a measure of force and weight is the product of the acceleration of gravity and an objects mass. The metric unit for measuring human mass is the kilogram (kg).
It depends on whether you want to measure mass or weight so your question needs to be more specific.