According to the APA Manual (Section 8.28 Written Material Without Page Numbers), you have three main options when quoting sources that do not have page numbers (webpages, eBooks, etc.). Use the option that will best help your reader find the quotation in the source:
According to the IceBridge Project leader, " in addition to the airborne and satellite measurements, scientists will be out on the ice taking height and density measurements as well" (Gray, 2019, para. 6). Source
Medical consensus is that the flu is spread "mainly by tiny droplets made when people with flu cough, sneeze or talk" (Centers for Disease Control and Prevention, 2019, How Flu Spreads section). Source
Research has shown that an average of 8% of the U.S. population experiences flu symptoms each flu season," with a range of between 3% and 11%, depending on the season" (Centers for Disease Control and Prevention, 2019, "How Many People" section). Source
One of the basic principles for citing is "to cite a specific part of a source" by including "an author–date citation for the work plus information about the specific part."
There are many possible "specific parts" to cite, including pages, paragraphs, sections, chapters, video time stamps, and slide numbers in PowerPoint presentations.
For examples, see Citing Specific Parts of a Source.