Most PC emulators, certainly the big three of VBA-m, mgba and no$gba, support codes of the major styles
http://vba-m.com/
https://mgba.io/
http://problemkaputt.de/gba.htm
Some of the android and such emulators might not have support for codes. Fortunately you can hardpatch codes into games
http://gbatemp.net/threads/gba-auto-trainer-maker-gbaatm.99334/ is the main one for this sort of thing these days.
Ignoring the hardpatching stuff then how you would do it varies.
If you have something like
https://filetrip.net/gba-downloads/...eats-databases-4-27-09-with-names-f31444.html
It should be fairly easy and the emulators will take codes in a menu somewhere for them.
If you have the encrypted codes they give out with the codebreaker and action replay then you might need some of the tools from
http://doc.kodewerx.org/tools.html#gba to sort them out.
I should also link
http://doc.kodewerx.org/hacking_gba.html which covers what GBA codes are encoded as and what they do. Can be useful if rather than 99 of an item via cheats you only want 10 as that makes play better for you.