Step to Convert OLM to PST Manually

Step 1. Setting up IMAP account using Gmail account

Launch the Gmail account by providing credentials to initiate the process to convert OLM to PST manually.
Click on the gear button from the top corner of Gmail and click on Settings option to convert OLM to PST file format.
From the Settings page go to the Forwarding and POP / IMAP tab.
Check your IMAP status, if it is disabled then enable it and Save the changes by clicking on the Save Changes button.
After following these sub-steps user will be able to create an IMAP account. After that, users need to install Outlook Mac with an IMAP mail account.

Step 2. Setup Outlook Mac with IMAP Mail Account

Open Outlook application on your Mac machine and go to Menu -> Tools -> Accounts and export Outlook OLM to PST
Enter the email address and password and click the Add Account button.
The IMAP mail account is configured and viewed on the Mail tab.
After applying these sub-steps, users need to create a Gmail label to synchronize between Outlook for Mac and IMAP account. To do this, follow the steps below.

Step 3. Create a Label in the Gmail Profile

First of all, open your Gmail account. Then click on the gear icon in the right side. Then, click on the Settings button.
Select the label and here and click on the Create New label and show checked in the IMAP box.
Go to your Mac Outlook and click Send / Receive.
Step 4. Transfer Emails from Mac Outlook to IMAP Mailbox

Open Outlook for Mac, right click on the mailbox item you want to transfer to Outlook for Windows.
Then choose Move -> Copy to folder.
Type the name of your IMAP folder and click Copy.
Click Send / Receive folder or Refresh on Gmail to update the mailbox.
Now all your copied mailbox data are synchronized to the IMAP mailbox folder.

I hope this manual method will be helpful!