Help! Mod Internal Camera

first, sorry english is not my native but I'll try to make it easy to understand.

so I have this app from my working place that need to click 'take picture' for completing work in progress.
when I click 'take picture' it'll open internal camera from the app itself.

I want to make this app can use external camera app, so when I click 'take picture' it'll prompt which camera app I want to use (camera app that already installed on my phone)

you can explain the how-to using english or indonesian.

thank you.