This page explains how to find the books cited by Stith Thompson in his Motif-Index of Folk Literature.
An entry from the Thompson Motif Index will look like this:
A 753. Moon as person
A753.1 Moon as wooer
A753.1.1 Moon abducts woman. Eskimo (Kodiak): Golder JAFL XVI 29.
Golder JAFL XVI 29 is the information you need.
Golder is the author's name.
Next is publication. It is abbreviated JAFL Thompson abbreviates most journal titles.
XVI is volume number.
29 is the page number where where the tale is referenced.
If the citation were to a book, the title of the book would be given, and you would search by the name of the author,
but because the citation is to a journal, you need to search by the journal.
J falls in the tab ranged I - M. ( i J k l m )
If you select that tab, you can either scroll to JAFL or you can do Ctrl + F JAFL.
You find this: *JAFL = Journal of American Folk-Lore. Boston, etc., 1888 ff.
Follow the link in the title to an online copy of the journal.
You still have to locate volume XVI (16) , open it, and then navigate to page 29.