hook when Module Addon Config Save

[mending3]

newb whmcs module addon dev. here.

I want to run a hook every time the Save Changes button clicked. how do I do it?
Complete step from how to create a hook + code sample would be hugely appreciated.
this is on admin/configaddonmods.php page

[mending3]

in the hook I want to be able to get the module addon info too

[mending3]

I asked this because I thought I need hook to do this. but the main issue is how do I run something when the Save button is clicked?