ChrisA is correct. The "USB to Host" connection on your PX-130 will only connect to a USB port on a computer. I'm not aware of any way to send the MIDI data out of your keyboard's USB port through a converter and directly into a 5-pin connector.
If you're using a PC you can control an external sound module "via" your computer using an intermediate software program and any USB/MIDI adapter. The routing would look something like this:
1) PX-130 MIDI into the computer via "USB to Host" connection.
2) Using MIDI Connection Center
you "connect" the MIDI In of the PX-130 to the MIDI Out of whatever USB/MIDI adapter you also have connected to the computer.
3) The USB/MIDI adapter is connected to the 5-pin MIDI input of your sound module.
The key, of course, is that the MIDI Connection Center is just re-routing the MIDI input from your keyboard right back out the USB/MIDI adapter into whatever sound module you have hooked up to the adapter.
Fortunately, any PC with 2 USB ports should work. You're only moving MIDI data around so a sound card isn't even needed.