Your question is too vague, the capacity of what?
Capacity of containers can be measured with volume, and units would be liters, quarts, or gallons. Capacity of computer systems is often measured in bytes, with units like megabytes or gigabytes. And capacity of some things like trucks and ships is often measured by weight, so the units would be kilograms, pounds, or tons.
Capacity isn't a unit at all. It's a characteristic, or a property of an item, which can be measured in whatever suitable unit. Capacity of batteries is measured in amp hours. Capacity of a gas tank can come in either liters or gallons.
A liter is typically used to measure liquid capacity, while a gram is used to measure mass. If you want to measure the volume of a liquid, you would use liters. If you want to measure the weight of an object, you would use grams.
Milliliters is the metric unit to use for the capacity of a thimble.
Capacity isn't a unit it is just a term that means how much a container holds. You can have metric units of capacity, such as Litres and Millilitres.
Metric
A millimeter is a unit of length, not a unit of volume or capacity. Perhaps you mean a cubic millimeter.
A litre is a unit of volume.
The unit is a litre.
decimeter is not related to capacity, it is in length.
(mAh) is the capacity. Click the link.
A metric unit of capacity or volume that is equal to 1000 milliliters is called 1 liter.
No, length.