U know 2 evolve onix u need 2 trade it with metal coat and krabby with king's rock but u don't know how 2 get it ? Then don't worry' Ill help you!

Metal Coat-Go to 5 island surf down u will see an island w/ 3 trainers u can either fight them or ignore them surf down again until you c a guy standing by a pillar land there and you"ll c a poke ball get it and then u have metal coat.
Kings rock go 2 7 island then down after a while you'll c rocks and broken 1s get the poke ball inside and then tada! u have the King's Rock.
Hope this helps' keep on training :)!