Move files to OneDrive for Business
If a user has a computer that includes many personal files, you should first move those files to OneDrive for Business:
Go to portal.office.com and sign in with the user's Microsoft 365 Business credentials.
Click the app launcher and go to OneDrive.
Choose Upload in the menu bar, and browse to the files you want to save.
To transfer the user profile and important files, you can also use a third-party tool, such as ForensiT. You should upload the resulting files in OneDrive for Business also.