[Grammar] What is correct ?

[emsr2d2]

No. The use of "if" shows uncertainty. You don't know if the person is going to be free so you are uncertain if they will be able to come.

The single most natural statement for this entire thread is "If you are free this evening, please come to [relevant place]".

 

[Tarheel]

So please tell me ..

I need to say the following with little uncertainty—so I used “Would” there. Is it correct? (No.)

If you would be free this evening, please come here.

I can't imagine anybody actually saying that. Also, if I did hear somebody say that my reaction would probably be: "What do you mean by If I would be free"? (That sentence has no meaning to me.)

Please note that I moved the question mark to its proper place. (The QMs don't like to be alone.)