This is a very rough receipt, letting you only provide the triggering tag of the flickr post. Unfortunately the tumblr-identity is not configurable in IFTTT - this would have been the second configurable option, otherwise.
If
New public photo tagged
This Trigger fires every time you upload a new public photo to your Flickr photostream with the tag you specify.
Fewer details
Explore more great ways to automate Flickr and Tumblr (legacy)