AutoCorrect entries -- where are they kept in Word 2016?

No, you can't rename your .acl file to use with the AutoCorrect template. You would have to run the equivalent program for Word 2003 from http://www.word.mvps.org/FAQs/Customization/ExportAutocorrect.htm in order to get a backup document in the correct format.

You may be able to substitute your 2003 .acl file for the one created by Office 2016. I don't think the file format has changed, but I'm not sure of that. It's worth a try, though.

With all Office programs shut down, start File Explorer. Type or paste into the address bar the path

%appdata%\Microsoft\Office

(The "environment variable" %appdata% automatically expands to the hidden AppData folder in your Windows profile.)

In the Office folder, you should see a file named MSO1033.acl, which is the AutoCorrect file for English (US). If your default language is something else, in the following instructions you must substitute the one with the correct locale ID number.

Move the MSO1033.acl file to a different folder, so you can move it back again if the procedure doesn't work.

Now copy the old .acl file into the Office folder, using the same name as the file you moved out.

Start Word and/or another Office program and look in the AutoCorrect Options dialog. If you see the complete list of entries that you expect, you're in luck. Otherwise, bring the original Office 2016 .acl file back into the Office folder and start adding entries the hard way.