Based on the info you've presented, its "cross your fingers and hope"
Can you tell us anything further about the motor, motor kit? Even a manufacturer could help.
My ebike kit used 7 pin DIN connectors with a screw-on barrel lock ring. The battery connectors were generic automotive spade connectors.
If you're choosing a connector, then voltage and current (ie wattage) is relevant, as is whether you want to hot-connect them. Plus you need something that is water resistant and vibration tolerant. (note spade connectors are neither of these... guess how I know that!)
Final thought - you're talking about a kit. In my mind a kit comes with everything you need to do the job, possibly excluding batteries themselves. However any parts not included will be common and well-described.
And what's wrong with a splice? A properly-done connection will outlive the wire.