"Find my iPhone" is turned off and I lost my phone.

Sorry, but you cannot remotely power up the phone. Here are your options.

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Find My is the very mechanism that connects the lost device to iCloud and allows for remote commands. Without it, there is no way to send any remote commands to the device, nor for the device to send any information to your account.

And a device that is powered off is completely inert. It cannot receive any command, nor execute any commands anyway. It has to be powered on and booted into a functioning operating system to do anything.

So what you’re asking for is technically impossible. Just as you cannot remotely power on a computer unless it is physically connected to the internet using a cable (which carries a low power connection to enable the device remote wake command to activate the device). But a powered off electronic device with no physical connection to the internet or a telephone network is incapable of doing anything.