Is a USB/USB cable the recommended way of connecting the two devices
No, not if you're trying to get the display of the laptop onto the TV. A USB port doesn't carry monitor signals.
are there reasonably priced adapters to convert FireWire 400 to HDMI
Firewire is also not a monitor signal. It can be used to transfer video information but afaik it's a completely different format to HDMI. I've not seen a device that converts firewire video to HDMI.
From your given ports the only way I'm aware of connecting your laptop to your tv would be with a VGA to HDMI adapter. VGA to HDMI adapters do exist at a reasonable price point, eg. https://www.jaycar.com.au/vga-to-hdmi-with-audio-adapter-usb-powered/p/AC1719?utm_campaign=redirect&utm_source=AC1639r&utm_medium=web
Maybe if you post the model of your laptop someone could confirm if it has a displayport capable of being adapted to HDMI. Not all displayport sockets can be converted to HDMI, even if the socket is electrically compatible with the adapter they still need to output the correct signal.