If you absolutely must download firmware, ignore random Google results and go straight to the tech community hubs:
: Flashing firmware usually wipes the device entirely. If the tablet still turns on, sync your photos and documents to Google Drive first.
If your tablet just needs an update, go to instead of manually flashing.
: For older or discontinued models, developers often upload firmware to community sites like NeedROM or the XDA Forums. These are vital if you are looking for specific "stock ROMs" to flash via a PC.