Neutrophils can be a bit tricky based on their granularity… so I would first apply a Gaussian - to try to deal with that. In any case - you will have trouble delineating them when these cells cluster.
I just ran these simple steps as a starting-off point for you - but for sure, other experts on here will have more refined methods I’m sure. For example - I set the Otsu threshold to grab all pixels above ~4900-5600 (should play with this a bit yourself to see - or Auto Threshold methods) and the 50-200 range may not be the best size cut-off - you’ll have to play and bit to see what works best.
run("Gaussian Blur...", "sigma=1");
run("Convert to Mask");
run("Analyze Particles...", "size=50-200 display exclude add");
roiManager("Show All with labels");
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