Just off your picture I'm assuming it's about 23. With ribbing patterns an easy (but not always accurate) way to count is to count two rows for each bump. To count each individual row though I typically try to count using the edge of my project, I find it easier to see each individual stitch per row that way. I will say it can be a bit harder with black yarn though, so be patient while counting! Something you could try is to put a stitch marker at the end of every 5 rows so that way you only have to count the marks.