Your question, along with your situation is a very difficult one. The only way to receive a pardon is to request one from the head of the particular government under which you were convicted. That is, if you were convicted of a state crime, then you must request a pardon from that state's Govenor. If it was a federal crime, then you must request the pardon from the President of the United States. In general, pardons are VERY hard to get, and VERY rarely given.
There may be an easier way. That is to get the conviction "expunged". For example, in New York, where I practice, sometimes you can bring an action called a post-conviction motion pursuant to NYS CPL §440, in the Court in which you were sentenced, asking for the conviction to be "set aside". If you were successful with this type of motion, you may be able to petition for re-entry into the U.S. based upon the fact that reason for your deportation no longer exists.
Hope this helps. Best of luck.