Do you mean take three core from power supply to PIR then on to each light in turn and on to other PIR then back to power supply forming a complete loop???
Please need some help! Want to wire four outside bulkhead lights down the side of my house, controlled by two PIRs at either end of the building so that whichever end you approach from all four lights will come on. I.E each PIR should be able to turn on all lights. Power will come direct from CU.