How much money can I receive in benefits if I adopt my granddaughter she is 3years old now
I can't give you a definitive answer without much more information about your situation. Adopting a child wouldn't have any effect on your own benefit rate, but an eligible child can be paid an auxiliary benefit of up to 50% of the primary insurance amount (PIA) of a living parent who's drawing either Social Security retirement or disability (SSDI) benefits.
However, there is a family maximum benefit (FMB) that can be paid on any person's Social Security record, which could lower the amount of the child's benefit if other children or a spouse are already drawing benefits on the same account. Furthermore, there is a special formula for calculating the FMB on the records of people who receive SSDI benefits, which can in some cases limit auxiliary benefits to zero. Social Security would have the records needed to answer your question, so I would suggest that you contact them.