What you're looking for is a cable that lets you replace the stock radio antenna with the TV's antenna. So, you connect the F-Connector the TV Antenna, and then you plug in the Motorola to the back of the radio. This will allow the radio to the use the TV antenna that is directional instead of the stock antenna that is not.
Since FM Radio uses frequencies that are relative close the TV station frequencies, (actually it sits between the VHF and UHF bands) the TV antenna should be a close enough tune to be able to pick up better signals than the stock one they put on our trailers.
In theory, you should be able to even run it through the antenna booster, getting even more coverage, but I don't know the internal workings of the booster to backup that claim and I don't have the wires on hand (yet) to try it out myself.
There's no use crying over spilled milk, unless it's on your keyboard.