What should my settings be on my Nikon D40?

When I blow a picture up to an 8x10 or bigger it looks ugly because its all choppy looking. Any help is appreciated.

Added (1). I printed them as an 8x10 on Shutterfly, Walmart, Snapfish and anything over 8x10 comes up looking horrible.

Image Quality: JPEG Fine
Image Size: Large 3, 008x2, 000; 6.0MP
ISO Sensitivity: Auto
Noise Reduction: Off

Added (2). Here a picture I blew up to 8x10:

You should be shooting at the maximum resolution your camera is capable of.
Blow up to what size?
I'd like to see what you are seeing. It sounds to me that you are looking at it on the computer at larger than 100%.It would be easier to see your problem if you could put a photo (full size) in a flickr account and then give us the link to it.

My 8x10 pictures on my Nikon D40 are great

are you shooting on the largest and finest jpeg? If not, that's what you should always do.

If you are submitting a 3000x2000 pixel image to any of those printers, it should look fantastic. The 8x10 prints I have made from my D40 come out great.

If you are submitting the image from your Flickr account, the highest resolution you have up there's 540x720. This will not print out very nicely at 8x10.

BTW, the settings you listed look fine.

Besides being underexposed it should print beautifully. Who are you printing with? Try using www.mpix.com for much better results. I suspect that your print source is your problem. All of those are pretty low quality printers.