mine is a 910 and my awning is a 925 its a little big unless you raise the front up so you can walk under I have used t for 3 years and with no problem like 1 of your reply's better big then to small
Derek, you need a 31ft 8in awning but awning sizes are expressed in centimetres so you need to convert that measurement into centimetres. You could also measure the size yourself or check with one of the awning manufacturers to see what size they recommend. As you have given an imperial measurement I presume your caravan is fairly old as awnings went metric years ago.
Be aware that modern caravans have higher awning rails. Older ones sloped at the sides. Awnings now are made for the increased height. Vans have higher ceilings inside and bigger wheels all which makes them higher.
The awning needs to slope away from the caravan otherwise rainwater will form a pool dragging the roof down forming a huge swimming pool.