Setting up for a storm

[westevens]

We have a 36 foot jayco travel trailer weighing about 7000 pounds. I would like to use Earth anchors drilling them into the ground leaving about 6 inches visible then use either chain or heavy duty ratchet straps to loop around the top of anchor and around the frame and rear bumper.
The question I have, what length of an anchor would I need?
Thanks for your help