Use this type of adapter for converting a 2.5mm male audio jack going into your power box to use with a 3.5mm audio jack lead wire or accessory using a 3.5mm male plug-in wire.

It has a 2.5mm male end that pugs into the power box with a 3.5mm female on the other end.  Some of the popular power boxes, such as Rimba, the Coyote and Zeus use a 2.5mm entrance into the power box.