Whether or not you're even able to get the Memphis station depends on a lot of things, the height of your antenna, hills and trees between your antenna and Memphis, and possible interference from your local ABC station. The simple things to check are the connection and the direction of your antenna. Check out the antennaweb.org link above and see what direction you're antenna needs to be pointing. Using a compass (I spent a whopping $3 on mine) make sure the antenna is pointing in that direction. You'll also see the distance from your house to the Memphis stations.
If you do all that and it still doesn't work, then I would recommend getting a preamp (like the
CM7777) and/or getting additional height with your antenna with a tall mast. I'm guessing that you might have a small antenna if it's actually connected to the Dish Network satellite. Using a larger antenna (like my
CM4228) will be necessary to pull in stations from 50+ miles away. You won't be getting those with some tiny antenna.
If you do all that and the terrain between you and Memphis doesn't block the signal, then I would guess that you'd be able to get all their stations (assuming you're no farther than 70 miles away). There's a guy on avsforum who lives 70 miles away from my local TV channels, and he gets all our stations with the CM4228 and CM7777 on a 30-foot mast. He does live on top of a hill, which definitely benefits him. As long as you're not in a valley, then I think it would be possible to get the stations with a little bit of work.
One more thing I just remembered is to check to make sure all the Memphis stations you want are UHF. If any are VHF, then you probably won't be able to get them from that far away, but there's really nothing you can do about that. You could try a dedicated VHF antenna in addition to the UHF antenna, but VHF has a harder time with long distances and should've never been used after the digital conversion.