I converted (reverted) to islam when I was young by myself no witnesses alone. I do not know if I converted properly for one this always makes me question is it valid and also how many prayers and fasts should I make up for now am above 40 have prayed many and fasted many but I feel I should just make up for last 1X years to have a topped account of my obligations and do I include the mentsral days as well? Do I make up since 1X/1X years old to make sure I have no debts in those and leave upon my death on others for these when I can do my best to do these myself as these are my responsibilities. Please tell me so I can work on these things and if I am not been able to complete by my time to go, can any charities feeding homeless or anything can help on these to help me ? Please help answer these

You don’t have to make up any salat before converting to Islam. Allah takes care of that and nothing to worry about. You worry should be on any salat, fasting etc immediately you converted to Islam. Meaning salats after you converted and not salat before your conversion