Make Unity Online Shop PC not mobile

Hello guys, this is the first time I ask a question in here and my question is how to make a online shop in unity multiplayer like i have 3 Weapons in the shop I want to make the player if he want to buy it check if the money is enough if is not he must buy the money from transport the money from his Paypal account to my paypal account or transport the money from any way to pay to my bank or something like this just like crossfire game or wolfteam game something like these games

i am sorry if my grammar is wrong but i hope you understand me and i hope you help me because i really need that.

Thank You.