Macpro Additional HD's

i have bought an early 2008 macpro. it has a 2TB Hard drive that works perfectly. i have installed a 1.5TB 3.5 inch Drive, a 500GB 2.5 sata disk attached to a spacer to fit the cradle and a 1TB 2.5 drive. when i boot up all i see is the OSX drive.

it is running El Capitan

Thanks for any advice or signposting