internal/Get-OlaHRestoreFile.ps1

function Get-OlaHRestoreFile
{
<#
.SYNOPSIS
Internal Function to get SQL Server backfiles from a specified folder that's formatted according to Ola Hallengreen's scripts.
 
.DESCRIPTION
Takes path, checks for validity. Scans for usual backup file
#>

    [CmdletBinding()]
    Param (
        [parameter(Mandatory = $true, ValueFromPipeline = $true)]
        [string]$Path
    )
        $FunctionName =(Get-PSCallstack)[0].Command
        Write-Verbose "$FunctionName - Starting"
        Write-Verbose "$FunctionName - Checking Path"
        if ((Test-Path $Path) -ne $true){
           Write-Warning "$FunctionName - $Path is not valid" -WarningAction stop
       
        }
        #There should be at least FULL folder, DIFF and LOG are nice as well
        Write-Verbose "$FunctionName - Checking we have a FULL folder"
        if (Test-Path -Path $Path\FULL)
        {
            Write-Verbose "$FunctionName - We have a FULL folder, scanning"
            $Results = Get-ChildItem -Path $Path\FULL -Filter *.bak
            $results = @($results)
        } else {
            Throw "$FunctionName - Don't have a FULL folder"
        }
        if (Test-Path -Path $Path\Log)
        {
            Write-Verbose "$FunctionName - We have a LOG folder, scanning"
            $Results += Get-ChildItem -Path $Path\LOG -filter *.trn
        }
        if(Test-Path -Path $Path\Diff)
        {
            Write-Verbose "$FunctionName - We have a DIFF folder, scanning"
            $Results += Get-ChildItem -Path $Path\DIFF -filter *.bak
        }

        return $Results
}