Read file and then replace word from csv file

i want replace words in config files, replace valor value in csv file example:

user      new user

abc        qwr

wer       123456

i want search word  "abc" , replace "qwr"

i write not know how add

$configfiles=get-childitem . *.config -rec
foreach ($file in $configfiles)
{
$file.pspath >> log.log
$a= "" + $file.pspath + ".bkp"
cp $file.pspath $a
(get-content $file.pspath) |
foreach-object {$_ -replace "decchi", "mono"} |
set-content $file.pspath

}

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adecchi

can try , explain little better?  once run replace have write data file.  more exact explanation of problem helpful.

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hope helps! jason

Windows Server  >  Windows PowerShell