The solution discussed here uses Node-Red.
The first thing to do is set-up a Node-Red server on your network and install the Blynk plug-in (contrib) for whatever version of Blynk you are using.
I’d also recommend setting-up the Mosquitto MQTT broker on the same server, and removing all Blynk code from your devices and using MQTT messages to control those devices.
Once you have that set-up and working then you can add-in the Alexa functionality.
I’ve recently migrated to the node-red-contrib-virtual-smart-home plug-in which is much easier to use and (so far) is much more reliable than the node-red-contrib-alexa-home-skill that I was using before.
This plug-in also allows a much wider range of device types to be used.
Pete.