The cable in the trailer is most likely RG-59 This is not really recommnded for sat antennas but may work if not too long.. RG-6 is suggested.
Now... What I recommend
Run a cable (RG-6) from a handy Bulkhead connector you install on the service (Driver's) side of the trailer... To the Sat receiver compartment..
Then either run the coax out on the sat receiver (IF ANY) to either the center connction on the back of a wall plat (12 volt outlet... Antenna fitting,,, Switfch and LED,, likely near Main TV) or back to the PARK CABLE in Now the switch plate selects ANT/SAT.
NOTE:if you have only one TV just feed it with HDMI and forget that coax out to TV lead.
Note 2:There is a better (but more complex)option as well.
IF you want to use the existing cable.....
Remove wall plate (IF you have it, if not see BOMB below)
Remove center cable
Using a multi meter or other means insure it is the park-cable lead
IF so... Extend it to the LNB jack on sat receiver
And optionally... IF receiver has coax out..Run that back to the plate
Re-mount plate (You will need to modify to get cables in and out)
BOMB (Box of many buttons,,Properly called Matrix Switch)
Find the CABLE lead on the back..Treat as above..ONLY run the return lead to SAT.