Great question!
Where to find the page numbers will depend on the ebook platform, but we can look to a Sage ebook chapter as an example.
Sage offers a feature to show page numbers, which can be cited in the same way as a print resource.
For example, if you access this ebook chapter https://go.openathens.net/redirector/royalroads.ca?url=https%3A%2F%2Fmethods.sagepub.com%2Fbook%2Fthe-sage-handbook-of-visual-research-methods-2e%2Fi3013.xml, you'll see the option to show the page numbers near the top right (as illustrated in the below screenshot). You'll definitely want to use this option rather than the page numbers on the PDF if you chose to download the chapter, as the page numbering on the PDF may not be correct.
The RRU Writing Centre further suggests that if you want to cite chapters or sections instead of specific pages, you can, and they recommend this resource for a comparison of those different options: Citing Specific Parts of a Source. The RRU Writing Centre's FAQ: How do I cite an ebook without page numbers in APA Style? might also come in handy if you aren't able to find page numbers for a resource in future.