Coverting Feet Into Inc or Pixels for A Banner

Hello All

I need to make two banners one is 10ftX14ft and the other is 6ftX8ft. When I create a new doccument there is no option for feet.

I need to convert Feet into Inches or Pixels, how can I do that, So illustrator will except the size?

Anny help would be appreciated.

Thank You

Linda