When an electronic source lacks page numbers, you should try to include information that will help readers find the passage being cited. Use the heading or section name, an abbreviated heading or section name, a paragraph number (para. 1), or a combination of these.
According to Smith (1997), ... (Mind Over Matter section, para. 6).
Note: Never use the page numbers of webpages you print out; different computers print webpages with different pagination. Do not use Kindle location numbers; instead, use the page number (available in many Kindle books) or the method above.
Source: Purdue's OWL
Use chapter and paragraph instead, noted with ch. and para., respectively. Example: (Smith, 2015, ch. 3 para. 15)