Finding the necessary information for a journal reference can vary from journal to journal. For example, you may need to look on the spine or cover of the journal to locate the title, volume and issue; but sometimes all the information you need is visible in the article itself.
The image below shows the header of the first page of a journal article. You can use these buttons to see the reference elements defined:
This particular journal does not require part number details, and has provided all the information you require on the first page. The page range details are not shown so you will need to check the last page of the article for the final page number.
The Harvard reference for this article would be:
Hanna, F. (2005) Multiple myelomas in cats. Journal of Feline Medicine and Surgery. 7, 275-287.