How to save player's coins to database?

Hello, So I created a game and I enabled In App Purchasing service to let the player purchase game coins, but Its a very stupid idea when the player purchases the coins the coins save to playerprefs, so what I really want to say is that I want to save the coins to database like every other games and with user registration and login system, I searched everywhere but they don’t really talked about something like this please is there any tips?

I haven’t watched the full video but I think this should help. SAVE & LOAD SYSTEM in Unity - YouTube