Use network upload to import your organization's PST files to Office 365
Before you begin.
Step 1: Copy the SAS URL and install AzCopy.
Step 2: Upload your PST files to Office 365.
(Optional) Step 3: View a list of the PST files uploaded to Office 365.
Step 4: Create the PST Import mapping file.
I hope this information on PST to Office 365 migration is helpful.