I have an YAMAHA MX61 and a Yamaha Digital piano P-115.  I WANT TO KNOW HOW CAN I TRANSFER MY SOUNDS FROM THE MX TO THE P-115… WHAT CABLES I NEED? DO I NEED TO USE A COMPUTER OR NOT?  OR WHAT DEVICES I NEED TO DO THAT.... THE MX HAS USB TO HOST AND MIDI INPUTS AND THE PT-115 HAS ONLY USB TO HOST.  THANKYOU

not possible.
only if you want to play with Yamaha p115 like electric guitar or new piano sounds-you can plug I pad to you yamaha p115 and use very good programm Sample tank (from IK multimedia). check how does it sound in youtube

I’m not sure about what you mean when saying “transfer sounds from the MX to the P-115”, but if you’re asking how to use the P-115 keyboard to play the MX sounds via MIDI, it’s not possible to do it directly because the P-115 has no MIDI terminals. But you can actually do it using a computer, connecting both the MX and the piano via USB to your computer and then using some suitable software to manage midi input/output ports such as MidiOX. You have to select your P-115 as the MIDI input and the MX as the MIDI output.