How to use devel on a taxonomy term page to see available nid's?
Terms have a term ID number (tid) and nodes have a node id number (nid). Terms are applied to nodes so nodes can be associated to terms and vice versa.

Devel module can show the structure of a taxonomy term. To achieve this:


Download and enable the devel.module
Ensure you are logged in with a user who has the Access developer information permission
Browse to the taxonomy term you want to inspect
Click the Devel tab if it is visible


If it is not visible, that is likely either a permissions issue or a theme issue - to fix a theme issue you could try changing to a core theme like Bartik

Then you should see some output like this: 
You can click tokens or Render or other sub-tabs as well
This shows the tid and other values associated with the term, but not the nid of nodes associated with the term