The custom payment methods are saved in the old version installation folder: 

 C:Program Files\ShopFactory V8\ShopFactoryPayment Methods  

So the solution is to copy and paste the custom payment methods XML files from - 

 C:Program Files\ShopFactory V8\ShopFactory\Payment Methods  

To the new version installation folder:

 C:Program FilesShopFactory V10\ShopFactory\Payment Methods 

Please follow the steps below: 

- Close ShopFactory V10  

- Navigate to your old ShopFactory version installation folder V8 (for example)

- And then navigate to ShopFactory Payment Methods   

- You should find your custom payment method's XML files there as per screenshot above 

- Copy all XML files – CTRL A and Right-click and then copy  

- Now, navigate to your new ShopFactory version installation folder- V9 (for example) 

- And then paste the files to ShopFactory Payment Methods as per screenshot below

- Now, open shop in ShopFactory V10 

- Re-setup payment method and make sure to tick “I would like to define my own payment methods” 

- Complete the setup 

-  And you will now see those custom payment methods and the custom payment can be modified  

-  Save and preview your shop. 

-  Place a test order to ensure that you can complete checkout.

-  Publish your shop so that the changes are uploaded online.