In a large bowl with hand mixer or using a stand mixer add cream, confectioners sugar, vanilla and cinnamon
Beat until stiff peak form, about 3-4 minutes
In another bowl mix together pumpkin puree and condensed milk
Melt butter in saucepan over medium high heat
Add sugar, cream and vanilla and whisk until smooth and dissolved
Let come to a bubble and boil for 2-3 minutes
Remove from heat, whisk in salt, then allow to cool
To assemble cake layer about 1/2 cup whipped cream in the bottom of a 9x13 casserole dish
Top with one layer of graham crackers (6-7) then top with 1/3 of whipped cream, 1/2 of pumpkin and 1/3 of caramel, repeat
For final layer add cracker, whipped cream and caramel
Cover and refrigerate for at least 2-3 hours before serving
Refrigerate any leftovers