This is the most critical step. Installing firmware for the wrong model (e.g., a 40-inch LED vs. a 55-inch 4K UHD) can brick your television—rendering it a black, unresponsive paperweight.
If you cannot find the file via search, email Polaroid support directly. Provide your model number and serial number. Request the "Latest firmware for USB installation." They will often email you a Dropbox or Google Drive link. Polaroid Tv Software Update Usb