Office 365 already has all the features of Office 2019 already. Office 2019 will get a set of features of Office 365 up to a certain point.
To switch to the 64 bit version of Office, you will first need to uninstall Office 365 32 bit and any associated Office 32 bit components - since you might run in to errors.
Once you have done that, proceed to reinstall Office again, but this time, choose the 64 bit installer.
Step 1 - Sign in to download Office
Go to http://www.office.com and if you're not already signed in, select Sign in.
Sign in with the account you associated with this version of Office. This account can be a Microsoft account, or work or school account.
Forgot your account details? See I forgot the account I use with Office.
https://support.office.com/en-us/article/i-forg...
On the Office home page, do the following depending on your version of Office.
If you signed in with a Microsoft account, from the Office home page select Install Office > Install. (Office 365 subscribers should select Install again).
This begins the download of Office. Follow the prompts on your screen to complete the install.