HOW DO I UPDATE WORD AND EXCEL TO 64 BIT?

What version of Microsoft Office do you have?

Only the 2016 version is upgradable to 64 bit: https://support.microsoft.com/en-us/help/3187505/office-2016-for-mac-64-bit-upgrade

Earlier versions will need to be removed and replaced with a newer 64 bit compliant version. Later versions, (2019), are already 64 bit.

Just to add, you don't actually have to upgrade them to 64bit until Mojave is replaced.

Yes, the 2011 version will not work on macOS versions after Mojave.

For now it will continue to work.