I have laid out below one way of solving this kind of problem. You have your timeline right and I have reproduced it with the correct amounts. The way to discount your 30Ks is the same as discounting 1,500K if you do it this way. Basically, you need to compute a discount factor. To calculate this discount factor, you need to de-annualize your interest rate by dividing by 12 months. This amount is then compounded at each period. To help you understand, here is the formula I have in the first cell under Discount factor (C2):
As you can see. The annual rate is divided by 12, you add 1 to it and take the power of it in relation with the period. The first period has no discount factor given that no time has elapsed. Finally, note that I have subtracted 1 from the Discount factor so that you could see the relation between annual rate and effective rate but in reality the discount factor does not subtract 1 (see how in period 12 the rate is 8.30% instead of 8.00% ? that's the effective rate (EIR) instead of annual rate (APR)).
Finally, to calculate the discounted amount you need to divide the amount by its discount factor (in this case you would need to add 1 to it).
The final NPV is 46,474$, assuming there is no tax involved.