A Microsoft file hosting and synchronization service.
Hi Jane, and welcome to Microsoft Q&A.
Personally, since I periodically back up my OneDrive files to an external drive, I would unlink OneDrive from the current OneDrive folder and link it to a new, empty folder named "OneDrive" on my external drive. Then I would go to the OneDrive Settings > Sync and Backup tab > Advanced Settings and select "Download all files". Now that I have backed up all my OneDrive files to the external drive, I can sign into my other account and copy the files to the other account's OneDrive folder.
Here's another way to transfer files between accounts: How do I transfer files from an old OneDrive to another?
I hope that helps. Feel free to post back if you require further assistance.
Craig