How to find data center of my tenant?

Do you mean which server pod your instance is hosted? If that's what you mean, you can look at the URL of your Marketo instance to deduce the data center where your pod is hosted. It's not 100% clear, but here's what I know generally: 

Example: app-abc.marketo.com/#SLXXXXA1

The "App-XXX" portion of the URL indicates which server pod you're on. You'll see some abbreviations there and according to other posts on the community, here are most of them: 

SJ, SJX, or SJRCA=San Jose

AB=Ashburn, VA

ABD=Ashburn?

LON=London