How can I rid myself of a past juvenile / criminal record that was committed in Florida. pardon sealed expunge?

I have many felonies and misdemeanors from when I was 15 years old. I'd like them expunged, sealed, or (preferably) be given a pardon. I'd like a clean record so I can join the coast guard, what are the chances of getting pardon? Would getting them expunged FULLY eliminate the discrepancies from my record?