replace string in multiple files within a folder.

hi, im new to powershell, but i wanna create a program that can replace a string with what a user will input within multiple different files.

this is my code:

$NewString = Read-Host -Prompt 'Input New Name Please'
$scriptPath = split-path -parent $MyInvocation.MyCommand.Definition

$InputFiles = Get-Item "$scriptPath\*.md"

$OldString  = 'SolutionName'
$InputFiles | ForEach {
    (Get-Content -Path $_.FullName).Replace($OldString,$NewString) | Set-Content -Path $_.FullName
}

echo 'Complete'

but it will only change a certain file, how do i make it look through all files in the folder it is in, and change the oldstring with the newstring ?

EDIT:
This was my solution

# Path of the current folder
$path = split-path -parent $MyInvocation.MyCommand.Definition

#input from user, to replace with.
$NewString = Read-Host -Prompt 'Input New Name Please'

#What to replace
$OldString  = '%SolutionName%'

#find all items, go through them and make the changes.
Get-ChildItem -Path $path  | where {!$_.PsIsContainer} | foreach { (Get-Content $_).Replace($OldString,$NewString) | Set-Content -Path $_.FullName }


echo 'Action is complete '

Try using Get-ChildItem versus Get-Item. Get-Item is a single item versus Get-ChildItem is a collection of items matching a search. If you need to search subfolders, you can use the -Recurse switch

i have got it to loop through all files in the folder with forexample .md as file extension, but it ignores all the other files…

will this do that ?

Use -Whatif to display results without changing names.

Get-ChildItem -Path \\path\to\folder -Filter *.md -Recurse | 
Rename-Item -NewName {$_.Name -replace "$old","$new"} -WhatIf