I did the same, and decided to transfer 35k+ emails from a PC to Mac.
- Archive all of your email on your PC. It saves in the *.pst format.
- Copy the *.pst file(s) to your mac, doesn't matter where you put them, I just left them on the desktop since they were temporary.
- Download the free MS Office for Mac trial from Microsoft.
- Import the *.pst files into your Outlook for Mac.
- Export from Outlook in mbox format (you can just drag the folders from Outlook onto your mac desktop - they should save as mbox format.)
- Import the mbox files into your Mac Mail.
Worked perfectly for me. (Keep in mind, this was with the "full" downloaded version of the suite, not with Office 365. I'd assume that you can do the same with 365, but you'll have to check it out.)
If you need to just create spreadsheets / documents or use existing simple xls/x and doc/x files, there are a few free solutions which are easily researched online. I personally use NeoOffice and Google Docs. They are similar to MS Office, but there are definitely some compatibility issues, i.e., all the formatting does not transfer perfectly. There appear to be some functions that don't carry over from newer Excel versions also, same with Powerpoint. I didn't check Word.
There are two other options that I have considered.
You can purchase Office for Mac. I have looked into this, and (like anything else) there are conflicting reports online about how well it works. You can just search "Office for Mac" on this forum for example, and get a whole spectrum of opinions. I may buy it one of these days.
You can install Windows and Office proper on your mac, via bootcamp or VM software like Parallels. This is the cheapest and most effective option IF you own the MS licenses. This option would guarantee though that your Office docs would still work as they did on your PC, and the software functionality would also be the same. I purchased Parallels as part of a bundle, and installed XP and Office 2007 since I already owned them. I would like to update Excel though, so I may end up with Office for Mac and skip the VM solution altogether.