Am looking to sync my calendar in outlook 2007 to my windows phone 8.1 which is a Lumia 625
I would like some more information to help you better.
– Have you tried anything on your own to sync calendar?
– If so, what were the results? (Do reply with error messages, if any)
In the meantime, I would suggest you to refer to the suggestions posted in following support article from Microsoft and check if it helps.
I hope this information helps.