> I would of
> I may of
https://www.perfect-english-grammar.com/could-have-should-ha...
https://www.perfect-english-grammar.com/could-have-should-ha...
Anyway, it's "could/should/would have" which in its contracted form is "could've" / "should've" / "would've".
If you were going to only include a link, https://en.oxforddictionaries.com/usage/could-of-or-could-ha... would have been a better choice, for example.