Create App Service Plan

Login-AzureRmAccount
Set-AzureRmContext -SubscriptionId "your subcription id"
$ResourceGroupName='test-rg'
$Location='Southeast Asia'
$AppServicePlanName='testplan'
$functionplan=Get-AzureRmAppServicePlan -ResourceGroupName $ResourceGroupName -Name $AppServicePlanName -ErrorAction Ignore
if(($functionplan| Measure-Object).Count -eq 0)
{
    $functionplan=New-AzureRmAppServicePlan -ResourceGroupName $ResourceGroupName -Name $AppServicePlanName -Location $location -Tier "Standard" -WorkerSize "Small"
}