Often times, the article's ISSN is listed in the article's record in a database alongside the title, author, journal name, date, etc.
We'll try to collect screenshots of all the databases, but if we haven't gotten to your database yet, please try the following:
If that doesn't work, we recommend searching through Ulrich's!
In the JSTOR Database, Find a link next to the title of the journal, named "Publication Info." That will pop up the publication info where you will find the ISSN!
Once you select an article, notice the ISSN on the bottom on the detailed record page of the database.