Once the ZIP is created, right-click it and rename the extension from .zip to .sb3 .
You don't always need a dedicated online "converter." In fact, the most reliable way to turn a ZIP back into a Scratch project is by doing it manually. Zip To Sb3 Converter
The heart of the project containing all the code and logic. Once the ZIP is created, right-click it and
Ensure all your project assets and the project.json file are at the root of the ZIP folder. If they are buried inside another folder within the ZIP, Scratch won't recognize them. Ensure all your project assets and the project
Select all the individual files (not the parent folder), right-click, and choose "Compress to ZIP file".
All your costumes and sounds, usually named with long alphanumeric strings (MD5 hashes). How to Convert ZIP to SB3 (The Manual Method)
Ultimate Guide to ZIP to SB3 Conversion: Why and How to Do It