where is my storage space "

 My Dell Venue 5830 Pro is missing storage space.

It is a 32gig tablet but the hard drive says it's only got 14.2 gig.

It was there before but now it's not.

I did a full reset and wiped everything  but I still don't have the full storage. just 14 gigs, not 32

When I try to upgrade to windows 10 I get an error message . It says I need at least 15 gigs

That is stopping me from up-grading. The deadline is coming up and I want to get the "FREE " upgrade

Can anyone help me?

Thanks,

Don