This will erase your USB drive.
In macOS 10.14 and earlier, it’s in /Applications/Install Mac OS X Snow Leopard.app/Contents/SharedSupport/InstallESD.dmg . On modern Macs, you must use a legacy device. Mac Os X 10-6 Snow Leopard Download Dmg
Look for the "Retail DVD" image (Version 10.6 or 10.6.3). These are universal and work on most Intel Macs from that era. Avoid "Machine-Specific" restore discs unless they match your exact hardware model. How to Create a Bootable USB from the DMG This will erase your USB drive