How do I turn the n-ahead ARIMA predictions to undifferenced values?

#1
Hello everyone,

I`m doing a Monthly sales forecast based on some historical data. My question is when I do the Arima(p,d,q) and then I do forecast(arima_model) in order to get the fitted values, which are nicely following the historical data points, then If I take the mean values from the forecast func, which are the n-ahead predictions, they are negative and differenced, because I do d=2 for the Arima. Is there any chance to obtain a normal values for the means from the forecast function? My aim is to know the real sales for n-ahead periods. Thank you in advance!