If your intent is to be able to raise the camper to change a flat tire, like the 2nd poster mentioned, you will need a bottle jack that fits under the frame or other jacking point when the tire is flat. A 6 ton regular size bottle jack will work but you'll probably need a 2X10X10 board to keep the jack from sinking into the ground. You should include this board in your measurement.
The tall jack you purchased would be very unstable. Remember to chock tires or be hooked up to your tow vehicle while changing tires.