32-bit apps

You don't need to worry about 32-bit apps until the next OS after Mojave. All Apple apps are already 64-bit and third party apps will notify you of updates. You can find all 32-bit apps in Apple menu > About this Mac > System Report > Software > Applications.

-When opening an App for the first time on Mojave, it will tell you if its a 32 bit App and state it may not be able to run on a future version of macOS.

You can get a list of 32 bit apps by going into the Apple Menu->About This Mac->System Report->Applications. Look at the "64 Bit" column for each App, it is says "Yes" its 64 Bit, if it says "No" its 32 bit app.

More info here: https://www.macobserver.com/columns-opinions/dr-macs-rants-raves/mojave-macos-10-14-32-bit-apps/

Some 32 bit apps may be from Apple, and you would need to wait for Apple to update them.

3rd party Apps would need to be updated by their developers or deleted.

If the developers are no longer updating the app, then eventually deletion is the only option. Though for now, there is no pressing need to delete them.

See here for how to delete Apps: How to delete apps on your Mac - Apple Support

You don't need to delete them at this time. Not until Mojave is replaced. The vendors will have to update them.

You're welcome.