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Chemistry molar enthalphy help

So.. my teacher is confusing and barely explains stuff ...
Anyways, I need help understanding when to use what formulas. (below are 4 formulas)

"Q=mc(delta)t" - This is used to find Joules (heat?)- units are J or KJ.. etc (I feel like this formula is kindof useless though, because I've never been asked to just find the "KJ".. Rather it's usually the molar enthalpy... so I would just use the formula below.. But if I do get a question that only asks for the heat? I use it?.. actually I'm not too sure when to use this, because most of the time I use the one below or the formula after that. )
"n(delta)cHm=mc(delta)t - (This is used to find Molar enthalpy?)- units are KJ/mol
(delta)rH- n(delta)rHm - this is used to find just the enthalpy.. so wouldn't that mean I'm technically finding Q, but because I have the molar enthalpy I would use it?
Q= C(delta)t - used when theres no mass of water or some stuff? Idk? or when the word calorimeter appears? o_o.

So basically, I hate chem because of this unit.. why couldn't they just use the same things... like (delta)rH is the same thing as Q...?
And sorry if it's hard to read, Even I have a hard time reading it lol...