I've been using planet waves unbalanced cables.
My kurzweil pc3 says it has balanced outputs, my yamaha emx312sc has balanced inputs.
So I need an unbalanced cable.
Do I need stereo trs cable where it goes from L and R from my keyboard into 1 jack, or do I just need 1 trs?
Please could someone post a link to what I need please.
PS. My amps isn't stereo I don't think as there is no pan know.
Read this:
http://kurzweil.com/knowledgebase/pc3/audio_output/267/
57 Hammond B3; 69 Hammond L100P; 68 Leslie122; MS Low Pro/Pro 3T; Kurzweil PC3; GEM Equinox 88 and 76 key versions; Voce V5+; Neo Vent; EV ELX112P; GSI Gemini Desktop Module; 67 Howard Combo Organ; https://dyinbreedband.wixsite.com/dyinbreedband/home
If you have balanced signal processing on both sides you generally want to use balanced cables (not unbalanced). 
I have read the manual a bit - your mixer-amp seems to be stereo capable with some "hard-wired" panning.
Inputs 5/6 + 7/8 are dedicated for stereo instruments - keyboards etc. But... these stereo inputs are not balanced... 
So you can:
- use true mono setup (1 balanced TRS-TRS or TRS-XLR cable)
in this situation left main OUT from Kurz (made for mono setup) goes into 1 mono CH 1-4 on the mixer
- try "summed" mono setup (2 balanced TRS-TRS or TRS-XLR cables)
both main OUTs form Kurz (L+R) going into 2 mono channels (CH 1-4) on the mixer
- use true stereo setup (2 unbalances TRS-TRS cables)
both main OUTs (L+R) going into stereo pair 5/6 or 7/8
Assuming that your mixer-amp is not more than 3-5m from you, noise should be very low
also if using unbalanced connection.
I use unbalanced outpust forever and it´s never been a problem. Usually they are plugged into a DI-Box if necessary (humming, long distances, no other inputs than XLR present). No big deal, it´s standard for keyboards.
