How many star coins are there in Super Mario 3D land

Well for starters, I would usually go look for the little nooks and crannies in a level, such as a wall which may have bricks you can break with a tanooki suit or by crouching under small holes that lead to rooms(Usually they are 1Ups but they can be paths to coins). Next EXPLORE as i would climb the walls of levels and follow the paths until something appears, and always use the binoculars, as you can spot out toad, and when you zoom up to him, he will toss a coin and you can collect it at the designated area. There may be more ways, but these helped me find the majority of all the coins. Hoped this helped!

The only way I've gotten them to respawn is when I street pass with someone who doesn't own the game. When I street pass with a random person who hasn't played Super Mario 3D Land, I'll get a mushroom house instead of a new purple box room. Other then that I haven't seen them randomly respawn on their own.