A family of Microsoft word processing software products for creating web, email, and print documents.
The items in the Bibliography dropdown are all the same except for what word is used in the title. As a quick workaround, you can insert the item that says "Bibliography", delete that word at the top of the bibliography, and replace it with the word "References". Everything else will remain the same.
To restore the "References" item to the dropdown, first shut down Word. Using the Windows File Manager, click in the address bar near the top and type or copy/paste
%appdata%\Microsoft\Document Building Blocks\1033\16
and press Enter. (This assumes you're using US English, whose Language ID is 1033; if it's another language, find the decimal code for that language at https://www.voidtools.com/support/everything/language_ids/ and substitute it for the 1033.)
In that folder, delete the file "Built-In Building Blocks.dotx".
Restart Word, and click the Bibliography button. That will cause Word to copy the original Built-In Building Blocks file from Word's distribution folder, which is buried six levels below C:\Program Files. You should now see References among the items in the dropdown.