Unity Iap - Own Store Implementation

Hello,
Is there any example of implementation own store for Unity IAP Demo ? I found only few examples of code in documentation, but I am still a little confused.

Thank you

Can you elaborate what you are trying to do? Creating your own store and accepting and processing credit cards and handling fraudulent purchase attempts is a lot of work. And without a lot of volume, many if not most users will be reluctant to enter their credit card details for an unknown store. The documentation is here: Unity - Manual: Implementing a Store

It is for my website. Users will use credits, not real money.

I created the store interface by this - Unity - Manual: Implementing a Store
then custom module by this - Unity - Manual: Registering your store

But how can I actually use module alongside with default modules ?

If found I should call:

ConfigurationBuilder.Instance (MyCustomModule.Instance(), StandardPurchasingModule.Instance ());

I would like to ask where can I find the example of MyCustomModule.Instance() ?

The documentation you pointed to already has the example. An instance is just one of many of an entity. Like:

GameObject myNewGameObject = new GameObject();

I haven’t tested for the custom module instance. What are you exchanging for game credits?