Exporting emails from Outlook
First you will need to export your emails from your outlook account so that you can import them in your Gmail account.
Open the outlook desktop client.
Log in using your outlook account.
Click on File > Open & Export > Import/Export.
After clicking on export the import and Export Wizard will open. On the wizard Select Export to a file and then click next
Create a file of type option select Outlook Data File (. pst) and select the folder you want to export.
Note : In the Image attached we are exporting the Inbox folder
Enabling IMAP your Gmail account
To transfer emails to your Gmail account, you will first need to be able to log into the Outlook Desktop Client (Outlook's Desktop App) . After enabling Imap you should be able to use your Gmail account on the Outlook Desktop Client.
Click on an internet browser of your choice ( can be Google Chrome, Edge, Safari etc.) Google to Gmail.com.
Log into to google using your Gmail account.
Click on Settings > See all settings > Forwarding and POP/IMAP
On the Forwarding and POP/IMAP Enable IMAP and click on Save Changes
Importing emails to your Gmail account
Open the Outlook Desktop Client.
Click on File > Add Account
Enter your gmail and click on connect
Enter your information and then click next
After logging your Gmail account into the outlook app you might need to restart the Outlook Desktop Client
After you have restarted the desktop client, click on File > Open & Export > Import/Export
On the Import and Export Wizard select Import from another program or file
On Select file type to import from, choose Outlook Data File(. pst).
On File to Import select the file you exported from your outlook account and in options choose Replace duplicates with items imported
On Select folder to import from, Select Outlook data file and choose Import Items into the same folder as your gmail.
