The math part is reasonably straightforward.

First calculate the Future Value of $50K/yr with return "r" lasting 38 years. This gives the amount you would have in your account at the end of that time.

Then you need to calculate the Present Value of that Future Value. In your case, you have to discount the FV by 38+11=49 years, at some discount rate "i".

The hard parts are picking what to use for "r" and "i" - so you ask a good question. You might want "r" to represent the return you can expect on investing that money (assuming you will invest it), and "i" to be the inflation rate that gives you an idea of how much that result will buy in today's dollars.

A couple of defensible numbers, off the top of my head, are 8% for a long term return and 3% for inflation.

Depending on whether you assume the $50K is invested at the start or end of the year, the final answer would be ~$2.6-$2.8 million using the numbers above.

E.g., using Excel functions:

FV(8%,38,-50000,0,1) = $11,897,061

PV(3%,49,0,-11897061) = $2,795,218