We don't have enough time, or space to write it in.
All units measure or quantify a certain something.
All are units of volume.
All SI units are powers of 10. Multiplying by 10 will convert units.
They are all metric units of measure.
They are all units to measure length.
There isn't one except by converting all the dimensions in the definition of an ampere into cgs units.
The similarity of these two conversions alone is that -- both of these convert from a smaller unit to a larger unit, so the original number becomes a smaller number, and -- both of these are involved with US customary units of measure. They also have similarities to each other that are the same as their similarities to conversions of all kinds of units of measure, in any system of units ... into which I don't think I'll go just now.
That depends what you want to measure. Look up the list of SI units; basically all of them are used to "measure things". For example: meter to measure length square meter to measure area kilogram to measure mass newton to measure weight etc.
All light is measured in Lumens. If you're wanting to know the units of power consumption of an LED, it's measured in Watts (W). LED's have a very low wattage, about 0.001 W or 1 mW!
No. A centimeter is a measure of length. Any unit of measure that has a meter in it is a measure of length. For example, millimeters, meters, kilometers are all units of measure for length.
After converting all the measurements to the same units, you would use the Pythagoras Theorem.
A kilogram is a measure of mass while a centimetre is a measure of distance. The two measure different things and it makes no sense at all to try to convert from one to the other.