/execute at @a if block ~ ~1.81 ~ minecraft:bricks run scoreboard players add @a[dx=-30,x=6,dz=12,z=7] dummyCoins 1
This adds a score of 1 to dummyCoins that is then targeted by the other commands, without getting in the way of the players already stored coins

It will then chain onto:
/scoreboard players add @a[dx=-30,x=6,y=50,dy=20,dz=12,z=7] coins 1
This adds 1 coin to the players stored coins

then:
/execute at @a[scores={dummyCoins=1..}] run setblock ~ ~2 ~ minecraft:end_stone_bricks destroy
This then replaces the brick the player hit with end_stone_bricks, which is the "empty brick", meaning it cannot be hit again for a coin.

then:
/title @a title {"text":"+1 Coin.","color":"gold","bold":true}
This gives a lovely title telling the player they got a Coin

then:
/scoreboard players set @a[dx=-30,x=6,dz=12,z=7] dummyCoins 0
This last step resets the dummyCoins to let the player start the chain again when they hit they're next block.

I tried to add an addition of /playsound to better replicate the Super Mario coins but couldn't make it work, I think it was something to do with the command chain being too long, maybe you could fix it!