How do I convert Outlook for Mac Mails directly to .PST form

Question

Hi, I am currently running my gmail account in Outlook for mac 2015. I want to convert the outlook for mac files to .pst format so that i can shift all the emails from mac to windows. My email database is quite large so it's taking too long to upload when I sign in windows outlook. So I thought that i can shift the emails from mac outlook to windows outlook. Please help me find the solution. Thanks