When I say i3 4xxx, what I mean is an i3 with a 4 in that place in the model name. Some examples:
i3 4150, i3 4370, i5 4440, i5 4690, i7 4770, i7 4790K
The "4" means "4th generation", just like in an i3 6100, the 6 means it's 6th generation (and would not be compatible with a motherboard that takes 4xxx CPUs). You can use any CPU that has a 4 there.