Also, if you feel that you need Office for your Mac, they make both a "normal" (perpetual license) version (about to be upgraded later this year) and a "subscription" Office 365 version that will open all your migrated Office files. You might also explore whether you could get along with the free (to you) "iWork Suite" consisting of Pages, Numbers and Keynote.
There are also other free options such as Libre Office. Whatever choice you make, there will be some differences you will need to adjust to, but they should be fairly minor. Congrats on the new iMac!