Plugin Upgrade

I have a plugin working on version 4.40.3, now some of our new customers have latest version "4.5"
I created a copy from plugin and changed plugin framework version from .NET Core 5 to .NET Core 6 to be compatible with nopCommerce 4.5, then copied plugin project to nopCommerce plugins,
but I have some errors when build application like
* IPayment Interface not have CalculateAdditionalFeeAsync method "Its already exist on version 4.40.3"
I don't need to upgrade nopCommerce itself , I just need to upgrade the plugin, is there are any documentation or other way to upgrade the plugins

Thanks

HI you can use this document for the Upgrade of nopCommerce  it can helpful for upgrading the plugin

https://docs.nopcommerce.com/en/installation-and-upgrading/upgrading-nopcommerce.html

RE: "... not have CalculateAdditionalFeeAsync method "
Probably because the method was moved to OrderTotalCalculationService :

public async Task<decimal> GetAdditionalHandlingFeeAsync(...
       _orderTotalCalculationService.CalculatePaymentAdditionalFeeAsync

I've found that for me, the best way to handle plugin upgrades is to "diff" a similar core plugin to itself for different versions (e.g. in your case, maybe a Payment Method plugin like Nop.Plugin.Payments.Manual, diff from 4.40.3 to 4.50.x).  Then you can make similar changes to your plugin.