Okay----you need a lot more help than we can give you in this user forum. You do not say what your situation has been. Have you been receiving taxable income during all of that time? If so, you need a good local paid tax pro to help you sort out the situation. This is not a do-it-yourself project if you have not filed in over 20 years.
Why have you not filed a return since the 1990's? Has something changed recently?