If you are in the U.S., the short answer is, you can't, it probably isn't. The majority of states don't require registration, and in the few that do, you normally can't access the information.
After you report it to the police, you wait and hope.
If you're in a country which has registration, such listings are typically not made available to private citizens.
Realistically, you can't.
The owner of a registered Class III firearm, such as a machinegun, should have a copy of the registration paperwork from the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE, or ATF for short). In some cases, such as when an owner dies, the heirs may have difficulty locating the paperwork. The executor of the estate can contact the ATF, and they can conduct a records search. IF the firearm has already been registered, it may be transferred by the ATF to an heir without a transfer tax. IF the firearm is not already registered, it cannot BE registered, and must be surrendered to the ATF for destruction. STRONG NOTE OF CAUTION- Possessing an unregistered Class III firearm is a serious offense, punished by 10 years in prison. If you have a Class III firearm that you are unsure of it's legality, you should contact an attorney that is familiar with the National Firearms Act for assistance AT ONCE.
They can forbid you to possess any firearm.
They usually give you warnings
You can pawn a firearm which you own.. if you pawn a firearm which you do not own, the legitimate owner may report it stolen, and you will be prosecuted.
Paper work done IAW local, state or federal law.
Yes, but may not have access to the firearm (stored under lock and key that the felon has no access to)
If you have concealed carry permit for that state, yes.
STATE law does not forbid it- but it MUST be registered, both with the Federal BATFE, and the state.
Since there have been several different models of "Tommy Guns", you will need to find a Class III Dealer that can obtain the correct parts for the model gun in question. There is also the little issue of having ALREADY registered your full auto with the BATFE. If not already registered back in May 1986, it cannot be registered- and possession of an unregistered full auto firearm is good for 10 years in Federal prison, a fine of $10,00, and loss of your rights to ever posses ANY firearm.