Right-click the file and select 7-Zip > Open archive . This allows you to browse the file and folder structure internally.
Files with purely numerical names like this often appear in: 3187800576.7z
If you have 7-Zip installed, run 7z l 3187800576.7z in your terminal to list all contained files, their sizes, and original timestamps. Right-click the file and select 7-Zip > Open archive