I used turbo tax to calculate 2018 taxes. Was too late to efile so printed and mailed return. Received no confirmation of receipt. Need refund amount to check

Download the pdf.  You need to register a 2019 online account to access prior years
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/01/27010

You should have mailed certified with receipt for conformation.  The IRS "Wheres my refund" site is only for the current year which is now 2019 taxes.  I doubt that it will tell you about 2018 refunds any longer.