Currently, there’s no way to automatically combine individual Dropbox accounts.
The easiest way to combine individual accounts is to move all files and folders from the older account to the main one you want to use.
Can I merge multiple Dropbox Business accounts?
Unfortunately, you cannot merge individual Dropbox Business accounts. However, you can easily move files between accounts.
If you're a Dropbox team admin, you can merge two Dropbox Business teams.
How to transfer all files and folders to another account
Learn how to move files between two accounts.