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I want to use Needs to download the QuickReIm package to simplify the complex conjugation, but I keep getting errors:

here is the Command:

Needs["QuickReIm`"]

and here are the errors:

Get::noopen: Cannot open QuickReIm`.
Needs::nocont: Context QuickReIm` was not created when Needs was evaluated.

Do you know the reason? Where can I find different packages and their uses?

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    $\begingroup$ Is it in your Applications folder? $\endgroup$ – CA Trevillian Dec 28 '19 at 1:13
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    $\begingroup$ Needs does not download anything (please check its documentation). What it does is it loads a package, provided that that package is installed. Downloading the package and installing it is something you need to do yourself before the package can be used. "QuickReIm" is not a standard package. If you have a question about it, you should clarify where one can get this package. $\endgroup$ – Szabolcs Dec 28 '19 at 11:20
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Not sure about the package you're referring to, but after a quick search I found Quantum Methods with Mathematica (result 5) which gives the source code for their version of the QuickReIm package as

BeginPackage["QuickReIm`"]
Begin["`Private`"]
protected = Unprotect[Re, Im, Conjugate]
Conjugate[expr_] := expr /. Complex[x_, y_] :> x - I y
Re[expr_] := Expand[(expr + Conjugate[expr])/2]
Im[expr_] := Expand[(expr - Conjugate[expr])/(2 I)]
Protect[Release[protected]]
End[]
EndPackage[]

And then Needs["QuickReIm`"] evaluates without error.

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