Since you are seeing an ‘Engine’ folder I assume you’re looking at a packaged version of your game. (You would not be able to continue development from this, you’d need the project files)
If you can still find the .uassets in the content folder: You should create a new project, and then merge the ‘backup’ content folder into the new one. (If you’re seeing .pak files in the content directory that means you’re looking at a packaged version)
One important thing to know is that you can only open .uassets in the engine version they were created, or a future engine version.
For example, if your backup project was using 4.26, you can place/open them in a 5.x project, but you can’t use any UE versions prior to 4.26.