Then you are on your own, as there is no standard for that sort of
wiring. If there were, not many after-market installers would follow it
anyway. Usually, if you look under the dash, it is very obvious which
wires are not original to the car. To get easier access, try removing
the lower dash cover on the driver's side, as this is usually where that
sort of thing is tucked away. When hunting for wires in cars (and other
places) I sometimes use a fox and hound set. This is what phone and
network installers use. Clip the fox between ground and the live wire at
the release motor. Then use the hound / tracer to find the other end of
the wire.

Remember to put a relay in the circuit, the alarm unit can not drive the
release motor directly (unless it has a relay built in, which I have
never seen for the trunk release output).