You need a US immigration lawyer, more specifically one specialized in abandonment cases with a proven track record. A good lawyer will give you a consultation at a nominal fee to tell you whether it is worth pursuing. This is not a DIY job!

If you want to DIY, either apply for a returning resident's petition at your local US consulate, or fly to America, tell the POE inspector you are a permanent resident, and s/he'll put you in front of an immigration judge where you can argue your case. With either option, I'd bet money that you'll lose without a professional preparing your case.