Nikon SLR D3100 uv lens size?

What size uv filter lens do i need to get for the Nikon D3100 with 28-80mm lens.

The lens has a filter thread size of 58mm.

58mm I believe. To check for yourself look on the lens and you will see a circle with a line through it. Next to this symbol will be a number. That number is the filter thread size. The same is true for all lenses.

The filter size should be 58mm, like your 28-80mm.

Here's a post called 'Buying a Lens Filter for DSLR (with Amazon links) - http://www.the-dslr-photographer.com/2010/03/buying-lens-filter.html