Errors in listing AD groups for AD PCs - powershell

Question

I am writing a script for work and trying to determine why my code is showing errors. I am new to this coding and want to understand what is wrong.
The errors I get are from the tag .... PC listings in my .txt file.
Ex: Get-Content : Cannot find path 'F:\tag 77909' because it does not exist.
My confusion is that when I write-host after the .Replace code it prints correctly
Ex:You cannot call a method on a null-valued expression. + $Notags =$PC.Replace <<<< ("tag ", "PC")
+ CategoryInfo : InvalidOperation: (Replace:String) [], RuntimeEx
ception
+ FullyQualifiedErrorId : InvokeMethodOnNull
Last error I get is that it only prints out the last PC.... ID in my .txt file listing??? I am unsure why given I have a foreach loop
**MY CODE SO FAR:**
Import-Module activedirectory
$compImports = Get-Content "C:\Temp\temp\input.txt"
$groupExport = "C:\temp\temp\output.txt"
Clear-Content $groupExport
$Header = "PC Name" + "|" + "Group Name" + "|" + "Group Description"
#Write header
$Header | Out-File $groupExport -Append
#get PC tag listing
$PCs = Get-Content $compImports
#For loop to change all "tag " to "PC"
foreach($PC in $PCS)
{
$Notags =$PC.Replace("tag ", "PC")
}
#loop to get information and print it out
foreach ($Notag in $Notags) {
$computerobj = Get-ADComputer $Notag -Properties memberof
$computerobj.memberof | ? {$_ -match '^CN=APP.*'} `
| % {get-adgroup $_ -Properties name, description} | `
% {$computerobj.Name + "|" + $_.name + "|" + $_.description `
| Out-File $groupExport -Append}
}

Answer 1

I see at least one issue here
$compImports = Get-Content "C:\Temp\temp\input.txt"
...
$PCs = Get-Content $compImports
You are calling Get-Content twice which would generate the error you are seeing most likely.
Could be simplified as
$PCs = Get-Content "C:\Temp\temp\input.txt"
Your other error should go away as a result since $PCs should contain real data at that point.