I’m not sure if the question is “If you scaled up a US Quarter to the size of a Mario coin, how large would it be,” or “How big would a mario coin be in real life”, so I’ll answer both, and then some others.

In the original Super Mario Bros., coins are roughly the same size as Mario.

According to wikia, Mario is 155cm tall (or 5’ 1”). So a real world quartet the size of a Mario coin would be 5’ 1” tall. This also means if a Mario coin were the size of s quarter, and Mario’s size relative to the coin stayed the same, Mario would be .995 inches tall.

The coins are also roughly as thick as Mario’s hands are long. Given that Mario is three heads tall, and the length of his hands are about .75x the height of his head, the coins would then be 38 cm deep or 1’ 3”.

Assuming these coins are solid gold, we can figure out the value of each coin in real US money by finding the volume of the coin, determining its weight, and comparing that to the current price of gold.

Given the the coin is cylindrical, we can find the volume with V=πr2h. Given that equation, the coin would weigh 43,479,249.92 ounces, but the price of gold is measured in Troy ounces. Converting ounces to Troy ounces will give us 39629525 , and multiplying that by the price of gold, which according to APMEX is $1,293.70 USD, will give us the real world value of the coin, which is $51,268,716,492.50.

So a lot of money.