Microsoft Word.app is not optimized for my Mac

I am working in Word & a pop up came up as follows: " Microsoft Word.app is not optimized for your Mac and needs to be update. This app will not work with future versions of macOS and needs to be updated to improve compatibility. Contact the developer for more information." I looked online & see that I can upgrade to Office 2019. Does Apple still sell CD-s for Office? If I do not update now will I lose the contents of Word? Many thanks for your help!