Wireless 2.4GHz to Bluetooth?
No, you can't.

Just because two things run on the same frequency does not make them compatible. Bluetooth and Wi-Fi both run on 2.4GHz, but you can't connect a Bluetooth device to a Wi-Fi network because the speak different protocols. A microwave oven also runs at 2.4GHz, you can't connect that to your network either.

Your keyboard likely uses some proprietary communication protocol, which will be in no way compatible with Bluetooth.

The only way to convert the keyboard to Bluetooth would be to take it apart, remove whatever transceiver it uses (or somehow disable the circuitry if it is not a separate module). Then you would have to find a suitable Bluetooth transceiver which supports presenting itself as a keyboard, and then somehow connect it in to a keyboard circuitry which is probably completely undocumented with no information available as to how the circuit talks to the transceiver.

It is simply not worth trying to do. Go buy an actual Bluetooth keyboard as it's probably cheaper than finding the right sort of Bluetooth transceiver module, and definitely much easier.