Meter Group sensors like the Teros 12 come with either bare wires or 3.5mm stereo headphone jack plugs. Have you already purchased your sensors? If not, you can choose that option when you order. You can also request a custom cable length if you need longer cables than the default length, which I think is usually 3 meters on their soil sensors. Having them manufacture the sensors with extra cable length is highly preferred to splicing your own extensions on them. So depending on which cable termination you have on your sensor, you’ll need to figure how you want to connect them to your Arduino board. Are you using this setup indoors in a lab setting, or outside in the weather? How many sensors do you want to hook up to one Arduino board? How often are you going to take sensor readings? Are you going to be logging the data somehow? When you used the 10HS, did you use that with the Mega 2560, or something else?