I would say, honestly it depends. You need to write just enough to keep people reading, though the word count in Tapas is much lower than in other online writing sites, so I end up splitting what would normally be one chapter into two parts on Tapas.
However, there is really no standard answer. I try to aim for about 3,000 words a chapter in general and then split them into two or three parts on here.
For example. Chapter 1 of my book on Wattpad is 4,000-ish words, but on here I have chapter 1 split into two parts with 2k words in one and 1k words in the other.
If you have not already written out your chapters and are writing on here only, I would aim for about 800 - 1,000 words a chapter??
IDK if this helps 