My company is switching to SharePoint on premise. We got the O365 package and I was searching how could we create custom input form and confirmation form like with InfoPath 2013. Is there a way to edit that form for a list? How do edit Flows email template? Like with those approve and reject buttons.
Unfortunately, you can't convert or migrate from PowerAppas to InfoPath form.
Power apps is a cloud service that can't be used with on-prem like InfoPath, meanwhile, you can create a gateway to get data from on-prem to the cloud!
Therefore, you can't migrate PowerApps to InfoPath forms and you need to start your business logic from scratch using SHarePoint Designer workflow and InfoPath and that will require enterprise edition!
Regarding the ability to do the same business logic with InfoPath, I think you can BUT without the same simplicity and functionality and of course, there are more functionalities in InfoPath that not available in PowerApss and vice-versa.
You can also check The key differences between InfoPath and PowerApps.
So I suggest trying 3rd party tools like Nintex or K2 to build your forms and business logic in an effective manner but sadly, it would be costly!