Date Formula Issues (For Warranties)

I’m trying to set some automation for warranty dates that if there is nothing selected it leaves it blank. But if the warranty drop down is selected it will read whats in the Warranty Start Days and apply the correct length of time to the date for the expiration date.

Other than googling I don’t have much experience with coding. Sorry. Thanks for any guidance

IF(Warranty=BLANK(),BLANK(), 
IF(Warranty= 1 Year), DATEADD({Warranty Start Date}, 365, "day") 
IF(Warranty= 2 year), DATEADD({Warranty Start Date}, 730, "day") 
IF(Warranty= 3 Year), DATEADD({Warranty Start Date}, 1095, "day"))