You placed the file in the wrong SD card directory. Fix: Create the exact path: [SD root]\Garmin\Update\10R04_6953.upd (all caps for Garmin folder). The device will not look anywhere else.
For official guides and manual downloads, you can visit the Garmin Support Center . If you'd like to proceed, let me know: What is the unit in? Are you seeing a specific error code during the update?
: Updates can take a significant amount of time. Always ensure the device is connected to a stable power source to avoid corruption during the "upd" process.