Try these 3 tutorials.
The first is about units and scales, the second about dimensioning (and dimension scales), the third is about metric paper sizes and plotting to scale from modelspace.
https://www.cadtutor.net/tutorials/a...and-scales.php
https://www.cadtutor.net/tutorials/a...mensioning.php
https://www.cadtutor.net/tutorials/a...aper-sizes.php
If you need metric drawing templates/borders then you can download a set here:
http://www.cadeverything.com/help/sh...WING-TEMPLATES
Im intelligent enough to know that I dont know everything; but I'll tell you all about it anyway.