how to get a player's mouse with Filtering Enabled?

i was making a script where when a player clicks the textbutton, a blueprint of a block (the shape of the block, just half transparent and blue) will follow the player's mouse. i got it to work in test mode, and decided to test it in a server. all the part does is move to the center of the map, and stay there. i figured out that the problem was that i can't get a players mouse with a RemoteEvent

game.ReplicatedStorage.RemoteEvent.OnServerEvent:connect(function(plr)
	local mouse = plr:GetMouse()

does anyone know how i can accomplish this? i found another question on this site related to mine, and said to try using RemoteFunctions. i have some what of an idea on what they do, but do not know how to use them, or how they could help this situation in any way.