It’s easier to use their names

Deci = 1/10th
Centi = 100th
Milli = 1000th
Micro = 1,000,000th
Nano = 1,000,000,000th

Deca = ×10 Hector = 100 Kilo = ×1,000 Mega - ×1,000,000 Giga = × 1,000,000,000 Tera = × 1,000,000,000,000,000

Etc prefixing the thing being measured.

So you know what a centimetre, gigabyte, megaton, kilojoules, etc. are.

Other easy conversions too, like 1kg = 1L of water.

And it’s metre. Because a meter is a measuring device and all this shit is Latin (metrum) like proper science stuff be. Americans don’t even use it, so they can fuck off with their misspelling.

And that’s it. You now know the metric system. You probably now realise you’ve been using it all along for many things.