This guide will overwrite the BP_MainMenu widget in your project

Create a new SGKv2 project using the same engine version as your existing project uses, then open its project files and go to the Content/SurvivalGameKitV2/Blueprints/Widgets then copy the BP_MainMenu file.

Then open your projects files and go to the same folder, make sure your project isnt open in the engine, then paste the file into the folder.